JavaScript has both strict and type-converting comparisons:

• Strict comparison (using 3 equal signs like ===) checks for value equality without allowing for coercion
• Abstract comparison (e.g. ==) checks for value equality with coercion allowed

Here are some simple equality rules:

• If either value (aka side) in a comparison could be the true or false value, avoid == and use ===.
• If either value in a comparison could be of these specific values (0, , or [] -- empty array), avoid == and use ===.
• In all other cases, you're safe to use ==. Not only is it safe, but in many cases it simplifies your code in a way that improves readability.

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var a = "42";

var b = 42;

​

a == b;     // true

a === b;    // false