What does == mean in js

In JavaScript, == is a loose equality operator that compares the values ​​of two operands without comparing their types. It follows the following rules: Numbers and Strings: Convert strings to numbers for comparison. Boolean value: true equals 1, false equals 0. Object: Compares references to objects, not values. undefined and null: undefined is equal to null. NaN: NaN is not equal to any value.

The meaning of == in JS

In JavaScript, = = is a loose equality operator that compares the values ​​of two operands but not their types.

Comparison Rules

== Operators compare according to the following rules:

• Numbers and String: Convert a string to a number and then compare the numeric values.
• Boolean value: true is equal to 1, false is equal to 0.
• Objects: Compares references to objects, not their values.
• undefined and null: undefined is equal to null.
• NaN: NaN is not equal to any value, including itself.

Example

console.log("1" == 1); // true
console.log("01" == 1); // true
console.log(1 == true); // true
console.log(1 == "1"); // true
console.log(null == undefined); // true
console.log(NaN == NaN); // false

The difference between ===

also in JavaScript There is another equality operator ===, which performs a strict equality comparison, comparing both values ​​and types. Therefore, === is not affected by the loose comparison rules.

console.log("1" === 1); // false
console.log(1 === true); // false
console.log(null === undefined); // false

Usage Precautions

Since == is prone to produce unexpected results, it is recommended to use == when strict equality comparison is required. =. For example, when comparing objects, you should use === to ensure that the actual values ​​of the objects are compared, not their references.

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