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")); // NaNIf 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));
//1506729600000The 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")); //NaNAs 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")); //NaNAs you can see in the example above, if the number cannot be converted, NaN (Not a Number) is returned.
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