A detailed introduction to JavaScript strings-JS Tutorial-php.cn

Stringin JavaScriptis represented by characters enclosed in '' or "". The following article will introduce you to the relevant knowledge ofJavaScript strings. Friends who are interested should take a look.

JavaScript strings are represented by characters enclosed in '' or "".

If ' itself is also a character, it can be enclosed by "". For example, "I'm OK" contains the six characters I, ', m, space, O, and K.

What if the string contains both ' and "? It can be identified by the escape character \, for example: the string represented by

'I\'m \"OK\"!';

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The content is: I'm "OK"!

The escape character \ can escape many characters, such as \n represents a newline, \t represents a tab character, and the character \ itself must also be escaped, so \\ The character represented is \.

ASCII characters can be represented in hexadecimal format in the form of \x##, for example:

'\x41'; // 完全等同于 'A'

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can also be represented by \u

# represents a Unicode character:

'\u4e2d\u6587'; // 完全等同于 '中文'

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Multi-line string

due to multiple lines It is more troublesome to write strings using \n, so the latest ES6 standard adds a new method of expressing multi-line strings, using `...` to express:

`This is a

Multiple lines

String`;

Template string

To have multiplestrings To connect

, you can use the + sign to connect:

var name = '小明'; var age = 20; var message = '你好, ' + name + ', 你今年' + age + '岁了!'; alert(message);

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If there are many variables that need to be connected, it will be more troublesome to use the + sign. ES6 has a new template character. String, the representation method is the same as the above multi-line string, but it will automatically replace the variables in the string:

var name = '小明'; var age = 20; var message = `你好, ${name}, 你今年${age}岁了!`; alert(message);

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Operation string

Common operations on strings are as follows:

var s = 'Hello, world!'; s.length; // 13

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To get the characters at a specified position in the string, use an Array-like The index operation,index

starts from 0:

var s = 'Hello, world!'; s[0]; // 'H' s[6]; // ' ' s[7]; // 'w' s[12]; // '!' s[13]; // undefined 超出范围的索引不会报错，但一律返回undefined

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It should be noted that the string is immutable. There will be no errors in assigning an index, but there will be no effect:

var s = 'Test'; s[0] = 'X'; alert(s); // s仍然为'Test'

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JavaScript provides some common methods for strings. Note that calling these methods itself does not Will change the content of the original string, but return a new string:

toUpperCase

toUpperCase() Change to uppercase:

var s = 'Hello'; s.toUpperCase(); // 返回'HELLO'

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toLowerCase

##toLowerCase() changes a string to all lowercase :

var s = 'Hello'; var lower = s.toLowerCase(); // 返回'hello'并赋值给变量lower lower; // 'hello'

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indexOf

indexOf()会搜索指定字符串出现的位置： var s = 'hello, world'; s.indexOf('world'); // 返回7 s.indexOf('World'); // 没有找到指定的子串，返回-1

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substring

substring()返回指定索引区间的子串： var s = 'hello, world' s.substring(0, 5); // 从索引0开始到5（不包括5），返回'hello' s.substring(7); // 从索引7开始到结束，返回'world'

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