6️⃣

6.6 Number Methods

6.5 Number Methods

Number Methods and Properties

Primitive values (like 3.14 or 2014), cannot have properties and methods (because they are not objects).

But with JavaScript, methods and properties are also available to primitive values, because JavaScript treats primitive values as objects when executing methods and properties.

toString Method

The toString method returns a number as a string.

All number methods can be used on any type of numbers (literals, variables, or expressions):

let x = 123;
x.toString();            // returns 123 from variable x
(123).toString();        // returns 123 from literal 123
(100 + 23).toString();   // returns 123 from expression 100 + 23

toExponential Method

toExponential() returns a string, with a number rounded and written using exponential notation.

A parameter defines the number of characters behind the decimal point:

let x = 9.656;
x.toExponential(2);     // returns 9.66e+0
x.toExponential(4);     // returns 9.6560e+0
x.toExponential(6);     // returns 9.656000e+0

The parameter is optional. If you don't specify it, JavaScript will not round the number.

toFixed Method

toFixed() returns a string, with the number written with a specified number of decimals:

let x = 9.656;
x.toFixed(0);           // returns 10
x.toFixed(2);           // returns 9.66
x.toFixed(4);           // returns 9.6560
x.toFixed(6);           // returns 9.656000

toPrecision Method

toPrecision() returns a string, with a number written with a specified length:

let x = 9.656;
x.toPrecision();        // returns 9.656
x.toPrecision(2);       // returns 9.7
x.toPrecision(4);       // returns 9.656
x.toPrecision(6);       // returns 9.65600

valueOf Method

valueOf() returns a number as a number:

let x = 123;
x.valueOf();            // returns 123 from variable x
(123).valueOf();        // returns 123 from literal 123
(100 + 23).valueOf();   // returns 123 from expression 100 + 23

In JavaScript, a number can be a primitive value (typeof = number) or an object (typeof = object).

The valueOf method is used internally in JavaScript to convert Number objects to primitive values.

There is no reason to use it in your code.

Number Method

Number(true);    	  // returns 1
Number(false);      // returns 0
Number("10");    	  // returns 10
Number("  10");     // returns 10
Number("10  ");     // returns 10
Number(" 10  ");    // returns 10
Number("10.33"); 	  // returns 10.33
Number("10,33"); 	  // returns NaN
Number("10 33");    // returns NaN
Number("John");  	  // returns NaN

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5️⃣
6.5 String Methods

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