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Global JavaScript methods to convert variables to numbers

in JavaScript on August 7, 2020

Converting Variables to Numbers

There are 3 JavaScript methods that can be used to convert variables to numbers:

1. The Number() method

2. The parseInt() method

3. The parseFloat() method

These methods are not number methods, but global JavaScript methods.

Global JavaScript Methods

JavaScript global methods can be used on all JavaScript data types.

Number() Method

Number() can be used to convert JavaScript variables to numbers:


console.log(Number(true));         // 1
console.log(Number(false));        // 0
console.log(Number("1"));         // 1
console.log(Number("  1"));       // 1
console.log(Number("1  "));       // 1
console.log(Number(" 1  "));      // 1
console.log(Number("1.99"));      // 1.99
console.log(Number("1,99"));      // NaN
console.log(Number("1 99"));      // NaN
console.log(Number("John"));       // NaN

If the number cannot be converted, NaN (Not a Number) is returned.

We can use the Number() Method on Dates

It will convert a date into a number.


var date = new Date("2017-09-30");

console.log(Number(date));

//1506729600000

The Number() method above returns the number of milliseconds since 1.1.1970.

parseInt() Method

parseInt() method parses a string into a whole number.

You can pass the number with spaces too but only the first number is returned:


console.log(parseInt("1"));  //1
console.log(parseInt("1.99"));  //1
console.log(parseInt("1 2 3"));  //1
console.log(parseInt("1 string"));  //1
console.log(parseInt("string"));  //NaN

As you can see in the example above, if the number cannot be converted, NaN (Not a Number) is returned.

parseFloat() Method

parseFloat() method parses a string into a whole number just like parseInt() but it can return the float numbers if any.


console.log(parseFloat("1"));  //1
console.log(parseFloat("1.99"));  //1.99
console.log(parseFloat("1 2 3"));  //1
console.log(parseFloat("1 string"));  //1
console.log(parseFloat("string"));  //NaN

As you can see in the example above, if the number cannot be converted, NaN (Not a Number) is returned.

Sources

dreamhost

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