1. typeof（不能区分复杂类型）
console.log(typeof bool); //boolean console.log(typeof num); //number console.log(typeof str); //string console.log(typeof und); //undefined console.log(typeof nul); //object console.log(typeof arr); //object console.log(typeof obj); //object console.log(typeof fun); //function console.log(typeof s1); //symbol
2. instanceof（不能识别基础类型）
console.log(bool instanceof Boolean); // false console.log(num instanceof Number); // false console.log(str instanceof String); // false console.log(und instanceof Object); // false console.log(nul instanceof Object); // false console.log(arr instanceof Array); // true console.log(obj instanceof Object); // true console.log(fun instanceof Function); // true console.log(s1 instanceof Symbol); // false
3. constructor
- 有局限 => constructor可以被篡改，null、undefined没有construstor
console.log(bool.constructor === Boolean); // true console.log(num.constructor === Number); // true console.log(str.constructor === String); // true console.log(arr.constructor === Array); // true console.log(obj.constructor === Object); // true console.log(fun.constructor === Function); // true console.log(s1.constructor === Symbol); //true
4. Object.prototype.toString.call（全面可靠）
const isType = (value) => Object.prototype.toString.call(value).toLowerCase(); isType(null); // '[object null]' isType(undefined); // '[object null]' isType([]); // '[object array]' isType({}); // '[object object]' isType(1); // '[object number]' isType("1"); // '[object string]' isType(true); // '[object boolean]'
