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== vs === in JavaScript

By: Stella in Javascript Tutorials on 2023年04月25日 [フレーム]

In JavaScript, == and === are two comparison operators that are used to compare two values or variables.

The == operator performs type coercion before comparing the values, which means that if the operands are of different types, it will convert one or both of them to a common type before comparing. For example:

console.log(10 == '10'); // true
console.log(true == 1); // true
console.log(null == undefined); // true

On the other hand, the === operator does not perform type coercion and will only return true if the values are of the same type and have the same value. For example:

console.log(10 === '10'); // false
console.log(true === 1); // false
console.log(null === undefined); // false

In general, it is considered a best practice to use the === operator for comparisons to avoid unexpected results due to type coercion. However, there may be cases where the == operator is preferred, such as when checking for null or undefined values, where the two are considered equivalent.

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