Introduction to the method of determining whether a variable is an object or an array in JavaScript

1. Because whether it is an array or an object, the return value of the typeof operation is object, so there is a need to distinguish between array types and object types:

2. Fang 1: Through the length attribute: Generally, the object does not have a length attribute value, its value is undefiend, and the length value of the array is of type number

3. Disadvantages: Very impractical, when the object The attribute of length exists and its value is number (such as array-like), then this method is invalid and is not recommended to be used. Just take a look.

4. *Part 2: Judge the distinction through instanceof

5. 1.instanceof

var arr = [1, 2, 3];

var obj = {

name: 'lyl',

age: 18,

l: 'name'

}

console.log(arr instanceof Array); //true

console.log(obj instanceof Array) ; //false

2.constructor

var arr = [1, 2, 3];

var obj = {

name: 'lyl',

age: 18,

1: 'name'

}

console.log(arr.constructor = == Array); //true

console.log(obj.constructor === Array); //false

3.Object.prototype.toString()

var arr = [1, 2, 3];

var obj = {

name: 'lyl',

age: 18,

1: 'name'

}

console.log(Object.prototype.toString.call(arr) === '[object Array]'); / /true

console.log(Object.prototype.toString.call(boj) === '[object Array]'); //false

4. Array only Methods (such as: sort, pop, etc.)

var arr = [1, 2, 3];

var obj = {

name: 'lyl ',
age: 18,
1: 'name'

}

console.log(arr.sort === Array.prototype.sort); //true

console.log(obj.sort === Array.prototype.sort); //false

The above is the detailed content of Introduction to the method of determining whether a variable is an object or an array in JavaScript. For more information, please follow other related articles on the PHP Chinese website!