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Asked: 2022-08-17T15:24:09+00:00 In:

Which equals operator (== vs ===) should be used in JavaScript comparisons?

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Which equals operator (== vs ===) should be used in JavaScript comparisons?
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    3 Answers

    1. This answer was edited.

      equals operator (== vs ===) should be used in JavaScript comparisons:

      The strict equality operator (===) behaves identically to the abstract equality operator (==) except no type conversion is done, and the types must be the same to be considered equal.

      Using the == operator (Equality)

      true == 1; //true, because 'true' is converted to 1 and then compared
"2" == 2;  //true, because "2" is converted to 2 and then compared

      Using the === operator (Identity)

      true === 1; //false
"2" === 2;  //false
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    2. What is == in JavaScript?

      Double equals (==) is a comparison operator, which transforms the operands having the same type before comparison.

      So, when you compare string with a number, JavaScript converts any string to a number. An empty string is always converts to zero. A string with no numeric value is converts to NaN (Not a Number), which returns false.

      What is === in JavaScript?

      === (Triple equals) is a strict equality comparison operator in JavaScript, which returns false for the values which are not of a similar type. This operator performs type casting for equality. If we compare 2 with “2” using ===, then it will return a false value.

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    3. This answer was edited.

      Double equals (==) is abstract equality comparison operator, which transforms the operands to the same type before making the comparison.

      For example,

      5 ==  5       //true
'5' == 5      //true
5 == '5'      //true
0 == false    //true

       

      Triple equals (===) are strict equality comparison operator, which returns false for different types and different content.

      For example,

      5 === 5  // true
5 === '5' // false
var v1 = {'value':'key'};
var v2 = {'value': 'key'};
v1 === v2 //false
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