【源码共读】axios的46个工具函数

export default {
  isArray, // 判断是否是数组
  isArrayBuffer, // 判断是否是 ArrayBuffer
  isBuffer, // 判断是否是 Buffer
  isFormData, // 判断是否是 FormData
  isArrayBufferView, // 判断是否是 ArrayBufferView
  isString, // 判断是否是字符串
  isNumber, // 判断是否是数字
  isBoolean, // 判断是否是布尔值
  isObject, // 判断是否是对象
  isPlainObject, // 判断是否是纯对象
  isUndefined, // 判断是否是 undefined
  isDate, // 判断是否是日期
  isFile, // 判断是否是文件
  isBlob, // 判断是否是 Blob
  isRegExp, // 判断是否是正则
  isFunction, // 判断是否是函数
  isStream, // 判断是否是 Stream
  isURLSearchParams, // 判断是否是 URLSearchParams
  isTypedArray, // 判断是否是 TypedArray
  isFileList, // 判断是否是 FileList
  forEach, // 遍历对象
  merge, // 合并对象
  extend, // 扩展对象
  trim, // 去除字符串两边的空格
  stripBOM, // 去除字符串的 BOM
  inherits, // 继承
  toFlatObject, // 将对象转换为扁平对象
  kindOf, // 获取对象的类型
  kindOfTest, // 判断对象的类型
  endsWith,// 判断字符串是否以指定的字符串结尾
  toArray, // 将类数组转换为数组
  forEachEntry, // 遍历对象的键值对
  matchAll, // 匹配所有的字符串
  isHTMLForm, // 判断是否是 HTMLForm
  hasOwnProperty, // 判断对象是否有指定的属性
  hasOwnProp: hasOwnProperty,  // 判断对象是否有指定的属性
  reduceDescriptors, // 降低描述符
  freezeMethods, // 冻结方法
  toObjectSet, // 将数组或者字符串转换为类似`Set`的对象
  toCamelCase, // 将字符串转换为驼峰命名
  noop, // 空函数
  toFiniteNumber, // 将字符串转换为有限数字
  findKey, // 查找对象的键
  global: _global, // 全局对象
  isContextDefined, // 判断上下文是否定义
  toJSONObject // 将字符串转换为 JSON 对象
};

// utils is a library of generic helper functions non-specific to axios
const {toString} = Object.prototype;
const kindOf = (cache => thing => {
    const str = toString.call(thing);
    return cache[str] || (cache[str] = str.slice(8, -1).toLowerCase());
})(Object.create(null));

const {toString} = Object.prototype;
const kindOf = (thing) => {
    const str = toString.call(thing);
    return str.slice(8, -1).toLowerCase();
};

const kindOfTest = (type) => {
  type = type.toLowerCase();
  return (thing) => kindOf(thing) === type
}

const {toString} = Object.prototype;
const kindOf = (cache => thing => {
    const str = toString.call(thing);
    return cache[str] || (cache[str] = str.slice(8, -1).toLowerCase());
})(Object.create(null));
const kindOfTest = (type) => {
    type = type.toLowerCase();
    return (thing) => kindOf(thing) === type
}
/**
 * Determine if a value is an ArrayBuffer
 *
 * @param {*} val The value to test
 *
 * @returns {boolean} True if value is an ArrayBuffer, otherwise false
 */
const isArrayBuffer = kindOfTest('ArrayBuffer');

/**
 * Determine if a value is an Array
 *
 * @param {Object} val The value to test
 *
 * @returns {boolean} True if value is an Array, otherwise false
 */
const {isArray} = Array;

/**
 * Determine if a value is undefined
 *
 * @param {*} val The value to test
 *
 * @returns {boolean} True if the value is undefined, otherwise false
 */
const isUndefined = typeOfTest('undefined');
/**
 * Determine if a value is a Function
 *
 * @param {*} val The value to test
 * @returns {boolean} True if value is a Function, otherwise false
 */
const isFunction = typeOfTest('function');
/**
 * Determine if a value is a Buffer
 *
 * @param {*} val The value to test
 *
 * @returns {boolean} True if value is a Buffer, otherwise false
 */
function isBuffer(val) {
  return val !== null && !isUndefined(val) && val.constructor !== null && !isUndefined(val.constructor)
    && isFunction(val.constructor.isBuffer) && val.constructor.isBuffer(val);
}

/**
 * Determine if a value is a FormData
 *
 * @param {*} thing The value to test
 *
 * @returns {boolean} True if value is an FormData, otherwise false
 */
const isFormData = (thing) => {
  const pattern = '[object FormData]';
  return thing && (
    (typeof FormData === 'function' && thing instanceof FormData) ||
    toString.call(thing) === pattern ||
    (isFunction(thing.toString) && thing.toString() === pattern)
  );
}

/**
 * Determine if a value is a view on an ArrayBuffer
 *
 * @param {*} val The value to test
 *
 * @returns {boolean} True if value is a view on an ArrayBuffer, otherwise false
 */
function isArrayBufferView(val) {
  let result;
  if ((typeof ArrayBuffer !== 'undefined') && (ArrayBuffer.isView)) {
    result = ArrayBuffer.isView(val);
  } else {
    result = (val) && (val.buffer) && (isArrayBuffer(val.buffer));
  }
  return result;
}

/**
 * Determine if a value is a String
 *
 * @param {*} val The value to test
 *
 * @returns {boolean} True if value is a String, otherwise false
 */
const isString = typeOfTest('string');

/**
 * Determine if a value is a Number
 *
 * @param {*} val The value to test
 *
 * @returns {boolean} True if value is a Number, otherwise false
 */
const isNumber = typeOfTest('number');

/**
 * Determine if a value is a Boolean
 *
 * @param {*} thing The value to test
 * @returns {boolean} True if value is a Boolean, otherwise false
 */
const isBoolean = thing => thing === true || thing === false;

/**
 * Determine if a value is an Object
 *
 * @param {*} thing The value to test
 *
 * @returns {boolean} True if value is an Object, otherwise false
 */
const isObject = (thing) => thing !== null && typeof thing === 'object';

const {getPrototypeOf} = Object;
/**
 * Determine if a value is a plain Object
 *
 * @param {*} val The value to test
 *
 * @returns {boolean} True if value is a plain Object, otherwise false
 */
const isPlainObject = (val) => {
  if (kindOf(val) !== 'object') {
    return false;
  }
  const prototype = getPrototypeOf(val);
  return (prototype === null || prototype === Object.prototype || Object.getPrototypeOf(prototype) === null) && !(Symbol.toStringTag in val) && !(Symbol.iterator in val);
};

/**
 * Determine if a value is undefined
 *
 * @param {*} val The value to test
 *
 * @returns {boolean} True if the value is undefined, otherwise false
 */
const isUndefined = typeOfTest('undefined');

/**
 * Determine if a value is a Stream
 *
 * @param {*} val The value to test
 *
 * @returns {boolean} True if value is a Stream, otherwise false
 */
const isStream = (val) => isObject(val) && isFunction(val.pipe);

/**
 * Checking if the Uint8Array exists and if it does, it returns a function that checks if the
 * thing passed in is an instance of Uint8Array
 *
 * @param {TypedArray}
 *
 * @returns {Array}
 */
// eslint-disable-next-line func-names
const isTypedArray = (TypedArray => {
  // eslint-disable-next-line func-names
  return thing => {
    return TypedArray && thing instanceof TypedArray;
  };
})(typeof Uint8Array !== 'undefined' && getPrototypeOf(Uint8Array));

/**
 * Iterate over an Array or an Object invoking a function for each item.
 *
 * If `obj` is an Array callback will be called passing
 * the value, index, and complete array for each item.
 *
 * If 'obj' is an Object callback will be called passing
 * the value, key, and complete object for each property.
 *
 * @param {Object|Array} obj The object to iterate
 * @param {Function} fn The callback to invoke for each item
 *
 * @param {Boolean} [allOwnKeys = false]
 * @returns {any}
 */
function forEach(obj, fn, {allOwnKeys = false} = {}) {
  // Don't bother if no value provided
  if (obj === null || typeof obj === 'undefined') {
    return;
  }
  let i;
  let l;
  // Force an array if not already something iterable
  if (typeof obj !== 'object') {
    /*eslint no-param-reassign:0*/
    obj = [obj];
  }
  if (isArray(obj)) {
    // Iterate over array values
    for (i = 0, l = obj.length; i < l; i++) {
      fn.call(null, obj[i], i, obj);
    }
  } else {
    // Iterate over object keys
    const keys = allOwnKeys ? Object.getOwnPropertyNames(obj) : Object.keys(obj);
    const len = keys.length;
    let key;
    for (i = 0; i < len; i++) {
      key = keys[i];
      fn.call(null, obj[key], key, obj);
    }
  }
}

function findKey(obj, key) {
    key = key.toLowerCase();
    const keys = Object.keys(obj);
    let i = keys.length;
    let _key;
    while (i-- > 0) {
        _key = keys[i];
        if (key === _key.toLowerCase()) {
            return _key;
        }
    }
    return null;
}
const _global = typeof self === "undefined" ? typeof global === "undefined" ? this : global : self;
const isContextDefined = (context) => !isUndefined(context) && context !== _global;
/**
 * Accepts varargs expecting each argument to be an object, then
 * immutably merges the properties of each object and returns result.
 *
 * When multiple objects contain the same key the later object in
 * the arguments list will take precedence.
 *
 * Example:
 *
 * var result = merge({foo: 123}, {foo: 456});
 * console.log(result.foo); // outputs 456
 *
 * @param {Object} obj1 Object to merge
 *
 * @returns {Object} Result of all merge properties
 */
function merge(/* obj1, obj2, obj3, ... */) {
    const {caseless} = isContextDefined(this) && this || {};
    const result = {};
    const assignValue = (val, key) => {
        const targetKey = caseless && findKey(result, key) || key;
        if (isPlainObject(result[targetKey]) && isPlainObject(val)) {
            result[targetKey] = merge(result[targetKey], val);
        } else if (isPlainObject(val)) {
            result[targetKey] = merge({}, val);
        } else if (isArray(val)) {
            result[targetKey] = val.slice();
        } else {
            result[targetKey] = val;
        }
    }
    for (let i = 0, l = arguments.length; i < l; i++) {
        arguments[i] && forEach(arguments[i], assignValue);
    }
    return result;
}

/**
 * Extends object a by mutably adding to it the properties of object b.
 *
 * @param {Object} a The object to be extended
 * @param {Object} b The object to copy properties from
 * @param {Object} thisArg The object to bind function to
 *
 * @param {Boolean} [allOwnKeys]
 * @returns {Object} The resulting value of object a
 */
const extend = (a, b, thisArg, {allOwnKeys}= {}) => {
  forEach(b, (val, key) => {
    if (thisArg && isFunction(val)) {
      a[key] = bind(val, thisArg);
    } else {
      a[key] = val;
    }
  }, {allOwnKeys});
  return a;
}

/**
 * Trim excess whitespace off the beginning and end of a string
 *
 * @param {String} str The String to trim
 *
 * @returns {String} The String freed of excess whitespace
 */
const trim = (str) => str.trim ?
  str.trim() : str.replace(/^[\s\uFEFF\xA0]+|[\s\uFEFF\xA0]+$/g, '');

/**
 * Remove byte order marker. This catches EF BB BF (the UTF-8 BOM)
 *
 * @param {string} content with BOM
 *
 * @returns {string} content value without BOM
 */
const stripBOM = (content) => {
  if (content.charCodeAt(0) === 0xFEFF) {
    content = content.slice(1);
  }
  return content;
}

/**
 * Inherit the prototype methods from one constructor into another
 * @param {function} constructor
 * @param {function} superConstructor
 * @param {object} [props]
 * @param {object} [descriptors]
 *
 * @returns {void}
 */
const inherits = (constructor, superConstructor, props, descriptors) => {
  constructor.prototype = Object.create(superConstructor.prototype, descriptors);
  constructor.prototype.constructor = constructor;
  Object.defineProperty(constructor, 'super', {
    value: superConstructor.prototype
  });
  props && Object.assign(constructor.prototype, props);
}

/**
 * Resolve object with deep prototype chain to a flat object
 * @param {Object} sourceObj source object
 * @param {Object} [destObj]
 * @param {Function|Boolean} [filter]
 * @param {Function} [propFilter]
 *
 * @returns {Object}
 */
const toFlatObject = (sourceObj, destObj, filter, propFilter) => {
  let props;
  let i;
  let prop;
  const merged = {};
  destObj = destObj || {};
  // eslint-disable-next-line no-eq-null,eqeqeq
  if (sourceObj == null) return destObj;
  do {
    props = Object.getOwnPropertyNames(sourceObj);
    i = props.length;
    while (i-- > 0) {
      prop = props[i];
      if ((!propFilter || propFilter(prop, sourceObj, destObj)) && !merged[prop]) {
        destObj[prop] = sourceObj[prop];
        merged[prop] = true;
      }
    }
    sourceObj = filter !== false && getPrototypeOf(sourceObj);
  } while (sourceObj && (!filter || filter(sourceObj, destObj)) && sourceObj !== Object.prototype);
  return destObj;
}

/**
 * Determines whether a string ends with the characters of a specified string
 *
 * @param {String} str
 * @param {String} searchString
 * @param {Number} [position= 0]
 *
 * @returns {boolean}
 */
const endsWith = (str, searchString, position) => {
  str = String(str);
  if (position === undefined || position > str.length) {
    position = str.length;
  }
  position -= searchString.length;
  const lastIndex = str.indexOf(searchString, position);
  return lastIndex !== -1 && lastIndex === position;
}

/**
 * Returns new array from array like object or null if failed
 *
 * @param {*} [thing]
 *
 * @returns {?Array}
 */
const toArray = (thing) => {
  if (!thing) return null;
  if (isArray(thing)) return thing;
  let i = thing.length;
  if (!isNumber(i)) return null;
  const arr = new Array(i);
  while (i-- > 0) {
    arr[i] = thing[i];
  }
  return arr;
}

export function toArray(list, start) {
    start = start || 0
    let i = list.length - start
    const ret = new Array(i)
    while (i--) {
        ret[i] = list[i + start]
    }
    return ret
}

/**
 * For each entry in the object, call the function with the key and value.
 *
 * @param {Object<any, any>} obj - The object to iterate over.
 * @param {Function} fn - The function to call for each entry.
 *
 * @returns {void}
 */
const forEachEntry = (obj, fn) => {
  const generator = obj && obj[Symbol.iterator];
  const iterator = generator.call(obj);
  let result;
  while ((result = iterator.next()) && !result.done) {
    const pair = result.value;
    fn.call(obj, pair[0], pair[1]);
  }
}

/**
 * It takes a regular expression and a string, and returns an array of all the matches
 *
 * @param {string} regExp - The regular expression to match against.
 * @param {string} str - The string to search.
 *
 * @returns {Array<boolean>}
 */
const matchAll = (regExp, str) => {
  let matches;
  const arr = [];
  while ((matches = regExp.exec(str)) !== null) {
    arr.push(matches);
  }
  return arr;
}

/* Creating a function that will check if an object has a property. */
const hasOwnProperty = (
    ({hasOwnProperty}) => (obj, prop) => hasOwnProperty.call(obj, prop)
)(Object.prototype);

const reduceDescriptors = (obj, reducer) => {
  const descriptors = Object.getOwnPropertyDescriptors(obj);
  const reducedDescriptors = {};
  forEach(descriptors, (descriptor, name) => {
    if (reducer(descriptor, name, obj) !== false) {
      reducedDescriptors[name] = descriptor;
    }
  });
  Object.defineProperties(obj, reducedDescriptors);
}

/**
 * Makes all methods read-only
 * @param {Object} obj
 */
const freezeMethods = (obj) => {
  reduceDescriptors(obj, (descriptor, name) => {
    // skip restricted props in strict mode
    if (isFunction(obj) && ['arguments', 'caller', 'callee'].indexOf(name) !== -1) {
      return false;
    }
    const value = obj[name];
    if (!isFunction(value)) return;
    descriptor.enumerable = false;
    if ('writable' in descriptor) {
      descriptor.writable = false;
      return;
    }
    if (!descriptor.set) {
      descriptor.set = () => {
        throw Error('Can not rewrite read-only method '' + name + ''');
      };
    }
  });
}

const toObjectSet = (arrayOrString, delimiter) => {
  const obj = {};
  const define = (arr) => {
    arr.forEach(value => {
      obj[value] = true;
    });
  }
  isArray(arrayOrString) ? define(arrayOrString) : define(String(arrayOrString).split(delimiter));
  return obj;
}

const toCamelCase = str => {
  return str.toLowerCase().replace(/[_-\s]([a-z\d])(\w*)/g,
    function replacer(m, p1, p2) {
      return p1.toUpperCase() + p2;
    }
  );
};

const noop = () => {};

const toFiniteNumber = (value, defaultValue) => {
  value = +value;
  return Number.isFinite(value) ? value : defaultValue;
}

function findKey(obj, key) {
  key = key.toLowerCase();
  const keys = Object.keys(obj);
  let i = keys.length;
  let _key;
  while (i-- > 0) {
    _key = keys[i];
    if (key === _key.toLowerCase()) {
      return _key;
    }
  }
  return null;
}

const _global = typeof self === "undefined" ? typeof global === "undefined" ? this : global : self;

const isContextDefined = (context) => !isUndefined(context) && context !== _global;

const toJSONObject = (obj) => {
  const stack = new Array(10);
  const visit = (source, i) => {
    if (isObject(source)) {
      if (stack.indexOf(source) >= 0) {
        return;
      }
      if(!('toJSON' in source)) {
        stack[i] = source;
        const target = isArray(source) ? [] : {};
        forEach(source, (value, key) => {
          const reducedValue = visit(value, i + 1);
          !isUndefined(reducedValue) && (target[key] = reducedValue);
        });
        stack[i] = undefined;
        return target;
      }
    }
    return source;
  }
  return visit(obj, 0);
}