There are two operators for comparing values in JavaScript: strict equality === and “normal” (or lenient) equality ==. Many style guides (correctly) tell programmers to avoid lenient equality and always use strict equality. This post explains why.

The == operator will compare for equality after doing any necessary type conversions. The === operator will not do the conversion, so if two values are not the same type === will simply return false. Both are equally quick.

'' == '0'           // false
0 == ''             // true
0 == '0'            // true

false == 'false'    // false
false == '0'        // true

false == undefined  // false
false == null       // false
null == undefined   // true

' \\t\\r\\n ' == 0     // true

• What is the difference between == and ===?