Detailed explanation of conversion between JS numbers and strings-JS Tutorial-php.cn

Detailed explanation of conversion between JS numbers and strings

小云云

Release： 2018-05-31 09:06:17

Original

2620 people have browsed it

This article mainly brings you a brief explanation of examples of conversion between JS numbers and strings. The editor thinks it’s pretty good, so I’ll share it with you now and give it as a reference. Let’s follow the editor to take a look, I hope it can help everyone.

Convert string to number

1 parseInt() function

parseInt() function parses from the beginning of string and returns an integer
parseInt('123'): Returns 123;
parseInt('1234xxx'): returns 1234;
parseInt('123.456'): returns 123;
parseInt('1 2 3'): returns 1; in the case of string, since Will return the first number
parseInt('bb cc 12'): Return NaN; if the first string is not a number, return nan
parseInt('123' 321): Return 321;
parseInt( "AF", 16); returns 175; it will automatically convert binary hexadecimal to octal into numbers

If the number cannot be parsed, a NaN value will be returned. You can use the isNaN() function to Detection;

parseFloat() will only return decimals

2 characters preceded by "+"

var n =+"123": return 123

3 characters plus "*"

var n ="123"*1: return 123

4 Add string array splitting

var arr = str.split(", ") A string group is divided into multiple by using
b = a.join("-");- is the specified separator, you can convert the array into a string at will

5 Adding a string and a number returns a string

console.log(12+"12"):返回"1212"
console.log(&#39;12&#39; + &#39;34&#39;)返回&#39;1234&#39; 
console.log(&#39;12&#39; + 34 ) 返回&#39;1234&#39; 
console.log(12 + &#39;34&#39;&#39;）返回1234&#39; 
console.log(12 + 34 ) 返回46

Copy after login

6 When adding a string and multiple numbers, expand them with brackets

("<img src=&#39;images/" + 2 + 1 + ".jpg&#39;>") 返回("<img src=&#39;images/" + 21 + ".jpg&#39;>")

Copy after login

If you want to convert it to 3

("<img src=&#39;images/" + （2+1）+ ".jpg&#39;>") 返回("<img src=&#39;images/" + 3 + ".jpg&#39;>")

Copy after login

If it is preceded by the addition of numbers, you can add the numbers first

var a = 10 + 20 + &#39;abc&#39; + &#39;cd&#39;; 返回a的值为:30abccd

Copy after login

7eval()If you want to perform string operations

eval("x=10;y=20;document.write(x*y)")    返回200
document.write(eval("2+2"))　　　　　　返回4
var x=10
document.write(eval(x+17）　　　　　　返回27

Copy after login

Convert numbers to strings

1 tostring（）
n = 100x = n.toString() => "100"或是（100）toString()  //tostring（2/16/8）还可以实现进制的转化

Copy after login

2 Number + any string ""

var n = 1234;var nn = 1234+""
-------------------------------------------------

Copy after login

About the string

Determine whether the string contains and returns the subscript. If it does not contain, return -1

　var i = str.indexOf("x")

Copy after login

The string of the last subscripted string

　var i = str .lastIndexOf("")

Copy after login

Convert to uppercase and lowercase

str.toUpperCase() 转大写
　　str.tolowerCase() 转小写

Copy after login

Intercept string string.substr ("Start from", "Intercept a few" )

　str.substr(0,5)
<body>

Copy after login

Related recommendations:

Detailed explanation of the traps that are more likely to occur with PHP numbers and strings

PHP numbers and characters String ID mutual conversion function (similar to Youku ID)_PHP tutorial

JavaScript number and string conversion example_javascript skills

The above is the detailed content of Detailed explanation of conversion between JS numbers and strings. For more information, please follow other related articles on the PHP Chinese website!