To check if a variable is an integer in JavaScript, use the Number.isInteger() method. It returns true if the given value is an integer. Otherwise, false.

Number.isInteger(34)         // true
Number.isInteger(2e64)       // true

Number.isInteger('0')        // false
Number.isInteger(Math.PI)    // false
Number.isInteger(null)       // false
Number.isInteger({})         // false

Number.isInteger(Infinity)   // false
Number.isInteger(NaN)        // false
Number.isInteger(-Infinity)  // false

The Number.isInteger() method was introduced in ES6 to determine whether the passed value is an integer.

If the given value is an integer, it returns true. For non-numeric values, NaN, positive or negative Infinity, or even for an instance of theNumber class, it returns false.

The Number.isInteger() method will also return true for floating point numbers that can be represented as an integer:

Number.isInteger(2.0)                  // true
Number.isInteger(2.3)                  // false
Number.isInteger(new Number(2))        // false

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