用 apply 将数组各项添加到另一个数组
const array = ['a', 'b']; const elements = [0, 1, 2]; array.push.apply(array, elements); console.info(array); // ["a", "b", 0, 1, 2]
函数只执行一次
function once (fn){ let called = false return function () { if (!called) { called = true fn.apply(this, arguments) } } } function func (){ console.log(1); } //调用 let onlyOnce = once(func); // 测试 onlyOnce(); // 1 onlyOnce(); // 不执行
防抖
/** * 防抖 * @param {Function} func 要执行的回调函数 * @param {Number} wait 延时的时间 * @param {Boolean} immediate 是否立即执行 * @return null */ let timeout; function Debounce(func, wait = 3000, immediate = true) { // 清除定时器 if (timeout !== null) clearTimeout(timeout); // 立即执行，此类情况一般用不到 if (immediate) { var callNow = !timeout; timeout = setTimeout(function() { timeout = null; }, wait); if (callNow) typeof func === 'function' && func(); } else { // 设置定时器，当最后一次操作后，timeout不会再被清除，所以在延时wait毫秒后执行func回调方法 timeout = setTimeout(function() { typeof func === 'function' && func(); }, wait); } } Debounce(()=>console.log(1));
递归数组降为一维
let children = [1, [2, 3], [4, [5, 6, [7, 8]]], [9, 10]]; function simpleNormalizeChildren(children) { for (let i = 0; i < children.length; i++) { if (Array.isArray(children[i])) { children = Array.prototype.concat.apply([], children); simpleNormalizeChildren(children) } } return children; } console.log(simpleNormalizeChildren(children)); // [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
数组降维(二维降一维)
function simpleNormalizeChildren(children) { for (let i = 0; i < children.length; i++) { if (Array.isArray(children[i])) { return Array.prototype.concat.apply([], children) } } return children } let arrs = [['1'],['3']]; const arr = simpleNormalizeChildren(arrs); console.log(arr); // ['1','3']
使用可选链进行函数调用
function doSomething(onContent, onError) { try { // ... do something with the data } catch (err) { onError?.(err.message); // 如果onError是undefined也不会有异常 } }
检测数组对象中是否有空值
const data = [ { name:"maomin" }, { name:"" } ] const arr = data.filter(item => Object.values(item).includes('') ); console.log(arr.length>0?"有空值":"无空值"); // 有空值
计算数组中每个元素出现的次数
let names = ['Alice', 'Bob', 'Tiff', 'Bruce', 'Alice']; let countedNames = names.reduce(function (allNames, name) { if (name in allNames) { allNames[name]++; } else { allNames[name] = 1; } return allNames; }, {}); console.log(countedNames); // { Alice: 2, Bob: 1, Tiff: 1, Bruce: 1 }
按属性对object分类
let people = [ { name: 'Alice', age: 21 }, { name: 'Max', age: 20 }, { name: 'Jane', age: 20 } ]; function groupBy(objectArray, property) { return objectArray.reduce(function (acc, obj) { let key = obj[property]; if (!acc[key]) { acc[key] = []; } acc[key].push(obj); return acc; }, {}); } const groupedPeople = groupBy(people, 'age'); console.log(groupedPeople); // { // 20: [ // { name: 'Max', age: 20 }, // { name: 'Jane', age: 20 } // ], // 21: [{ name: 'Alice', age: 21 }] // }
将带有分割符的字符串转化成一个n维数组
const str = "A-2-12"; const str1 = str.split('-'); console.log(str1); const arr = str1.reverse().reduce((pre,cur,i) => { if(i==0) { pre.push(cur) return pre } return [cur,pre] },[]) console.log(arr) // ["A"["B",["C"]]]
