Detailed explanation of steps to use JS string method-JS Tutorial-php.cn

This time I will bring you a detailed explanation of the steps to use the JSstringmethod, and what are thenoteswhen using the JS string method. The following is a practical case, let's take a look.

1. Method reading instructions

Return value typeObject.Method name (parameter 1[, parameter two]);
Explanation:

返回值类型：指的是函数调用结束后返回的值的类型。 对象.方法名称：指的是调用方法。 参数列表：表示函数调用时传入的参数。[]表示可选参数，可写可不写。

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2. Stringattribute

Definition:By a pair of""or a pair of''Wrapped, it is a string composed of0 or more characters.
String length:

string.length;

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eg:

var str1="abc"; var str2=""; var str3=" "; console.log(str1.length);//3 console.log(str2.length);//0 console.log(str3.length);//1

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3.charAt

Function:This method returns the characterat the corresponding position of.
Syntax:string string.charAt(index);
Parameters:index refers to0 to string length-1is an integer.
Return value:Returns the characterat the corresponding position of thestring.

Note:

- 如果传入参数小于0或者大于 字符串长度-1，则返回空字串。 - 如果传入boolean值，如果为true，默认是转化为数字1，指到字符串第二个字符。如果为false，默认是转化为数字0，指到字符串第一个字符。 - 如果传入任意字符串，则指到字符串第一个字符。

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4.chatCodeAt

Function:Returns the Unicode value of the character corresponding to
Syntax:number string.charCodeAt(index);
Parameters:index refers to0 to string length-1is an integer.
Return value:Returns the Unicode valueof the character at the corresponding position in thestring.

Note:
If the incoming parameteris less than 0oris greater than the string length -1, an empty string will be returned. NAN is returned.

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4.fromCharCode

Function:Convert Unicode values into corresponding characters.
Syntax:string String.fromCharCode(index);
Parameters:index refers to passing in any integer.
Return value:Returns the stringcorresponding to theUnicode value.

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Small example of encryption and decryption

5.indexOf

Function:Returns the specified value string when calling this methodFirst timeThe position where it appears.
Syntax:number string.indexOf((searchValue [, fromIndex]));
Parameters:searchValuerefers to The string to find.fromIndexrefers to where to start searching. The default value is 0.
Return value:Returns a number.
Note:If it exists, the position will be returned, if it does not exist, -1 will be returned.

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5.lastIndexOf

Function:Returns the specified value where the lastof the stringappears when this method is called.
Syntax:number string.indexOf((searchValue [, fromIndex]));
Parameters:searchValuerefers to The string to find.fromIndexrefers to where to start searching. The default value is str.length-1.
Return value:Returns a number.
Note:If it exists, the position will be returned, if it does not exist, -1 will be returned.

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6.slice

Function:method extracts a part of the string and returns this new string(including the starting position, not including End position)
Syntax:string string.slice((star [, end]));
Parameters:star is Refers to the interceptionstarting position, end refers to the interceptionend position, the default is position 1 of the last character (the length of the string).
Return value:Return the intercepted string.

Note:

will not exchange parameter positions according to parameter size
If there are Negative values are processed from the end.-1 refers to the last element, -2 refers to the penultimate element.

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7.substring

作用：方法提取字符串中的一部分，并返回这个新的字符串（包含起始位置，不包含结束位置）
语法：string string.slice((star [, end]));
参数：star是指截取的起始位置，end是指截取的结束位置，默认为最后一个字符的位置+1 ( 字符串的长度 )。
返回值：返回截取后的字符串。

注意：

会根据起始位置和结束位置的大小先进行参数位置的变换
会把负值转换成0

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8.substr

作用:截取指定起始位置和长度的子字符串.
语法:string string.substr(start [, length]);
参数:start:截取的起始位置。length:截取的字符串长度，默认为字符长度。
返回值:返回截取后的字符串

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9.toLowerCase

1.toLowerCase
作用:把字符串全部转成小写
语法:string string.toLowerCase();
返回值:返回转成小写的字符串。

2.toUpperCase
作用:把字符串全部转成大写
语法:string string.toUpperCase();
返回值:返回转成大写的字符串。

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10.split

作用:通过一个指定的字符串把原字符串分割成一个数组。
语法:array string.split([separator] [, limit])
参数:separator是指分割符。limit指定最多分割的数量，可以理解为数组长度，默认为全部。
返回值:返回一个数组。
注意:当没有分割符的时候(没有传入参数)，整个字符串将作为一个整体保存到数组中。用分割符分割的时候，分割符会在被删除了在传入数组。