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JavaScript - Math.trunc() method example

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Created by:

Maison-Humphries

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The Math.trunc() method returns integer part of a number.

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console.log( Math.trunc(  5     )); //  5
console.log( Math.trunc(  3.14  )); //  3
console.log( Math.trunc( -3.14  )); // -3
console.log( Math.trunc(  0.123 )); //  0
console.log( Math.trunc( -0.123 )); // -0
​
console.log( Math.trunc( '+3.14' ) ); //  3.14
console.log( Math.trunc( '-3.14' ) ); // -3.14
console.log( Math.trunc(  NaN    ) ); //  NaN
console.log( Math.trunc( 'foo'   ) ); //  NaN
​
console.log( Math.trunc() ); // NaN

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1. Documentation

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Syntax	`Math.trunc(number)`
Parameters	`number` - integer or float number value (primitive value).
Result	Integer part of `number` value (primitive value). If `number` is `NaN` it returns `NaN`. If `number` is `-Infinity` it returns `-Infinity`. If `number` is `+Infinity` it returns `+Infinity`.
Description	`Math.trunc()` is a static method that takes one parameter and returns integer part of number passed as argument. Integer numbers are returned without any changes. Note: this method has been introduced in ES 2015.

2. Polyfill example

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This example shows polyfill solution for lack of the method.

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if (Math.trunc == null) {
    Math.trunc = function (v) {
        return v < 0 ? Math.ceil(v) : Math.floor(v);
    };
}
​
// Usage example:
​
console.log( Math.trunc(  5     )); //  5
console.log( Math.trunc(  3.14  )); //  3
console.log( Math.trunc( -3.14  )); // -3
console.log( Math.trunc(  0.123 )); //  0
console.log( Math.trunc( -0.123 )); // -0