6.6 Number Methods

6.5 Number Methods Number Methods and Properties toString Method toExponential Method toFixed Method toPrecision Method valueOf Method Number Method Previous Section

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

Previous Section

5️⃣

6.5 String Methods

⚖️

Copyright © 2021 Code 4 Tomorrow. All rights reserved. The code in this course is licensed under the MIT License. If you would like to use content from any of our courses, you must obtain our explicit written permission and provide credit. Please contact classes@code4tomorrow.org for inquiries.