How does JavaScript determine the type? (code example)

This article will introduce to you how to determine the type in JavaScript? (Code example) has certain reference value. Friends in need can refer to it. I hope it will be helpful to you.

The typeof method in JS can check the type of data, as follows:

console.log(typeof 2); // number
console.log(typeof "2"); // string
console.log(typeof true); // boolean
console.log(typeof [2]); // object
console.log(typeof {name:2});// object
console.log(typeof function(){return 2});// function
console.log(typeof new Date());// object
console.log(typeof null); // object
console.log(typeof undefined);// undefined

But typeof can only distinguish between numbers, strings, Boolean values, methods and undefined, other objects, arrays, dates, null, etc. are all objects, but they still cannot be distinguished.

We can use Object.prototype.toString.call to achieve this.

 var getType = Object.prototype.toString;
var res = getType.call(2);
res = getType.call("2");
res = getType.call(true);
res = getType.call([2]);
res = getType.call({name:2});
res = getType.call(function(){});
res = getType.call(new Date());
res = getType.call(null);
res = getType.call(undefined);

The output results are:

[object Number]
[object String]
[object Boolean]
[object Array]
[object Object]
[object Function]
[object Date]
[object Null]
[object Undefined]

This way, the data types in JS can be specifically distinguished.

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