JS string method

All string methods will return a new string , Instead of changing the original string .

Find string

indexOf(src,index)
Traverse from the beginning target character string , Find a match src The first occurrence of the index （ Location ）, No return found -1

lastIndexOf(src,index)
Traverse from the end target character string , Find a match src The first occurrence of the index （ Location ）, No return found -1

search(src)
and indexOf identical , It just doesn't have a second start position parameter .
String extraction

slice(start, end)
Extract from start Start to end The string content of , If end Greater than the total length of the string or omitted , Then extract start All subsequent strings , If a parameter is negative （ Negative values are not suitable for IE8 And earlier ）, Then count from the end of the string .

var str = "Apple, Banana, Mango";
var res = str.slice(-13,-7); //Banana

substring(start, end)
Be similar to slice(), However, input parameters with negative values are not accepted

substr(start, length)
Be similar to slice, The difference is that the second parameter is the length of the extracted part , If omitted , Is extracted directly to the end of the string ,start Support is negative .

charAt(index)
Returns the specified subscript in the string ( Location ) String , Compared with direct use str[index] The way to get characters is more secure , If it cannot be found, it will directly return an empty string , however str[index] Will return undefined, Simultaneous adoption str[index] Just read the string , Not through str[index] = ‘A’ Change the way index The value of the location .

charCodeAt()
Returns the... Of the specified index character in a string unicode code ;
String segmentation

split(str)
according to str Split strings into arrays , Omit separator , The returned array will contain index [0] The entire string in . If the separator is “”, The returned array will be an array separated by a single character

var str = "Hello";
var arr = str.split(""); ['H','e','l','l','o']
var str = "a,b,c,d,e,f";
var arr = str.split(); // arr[0] by "a,b,c,d,e,f"

String splicing

concat(str1, str2, str3…)
Concatenate multiple strings , It can also be used. + Operator implementation

Other functions

replace(target, src)
In the string target Replace the string with src character string , Only the first match is replaced and is not case sensitive , But the first argument supports regular expressions , That is, if you want to implement case insensitive replacement or replace all matching items , It can be solved by regularization .

str = "Please visit Microsoft!";
var n = str.replace(/MICROSOFT/i, "W3School");
var n = str.replace(/Microsoft/g, "W3School");

toUpperCase()
String capitalization
toLowerCase()
String to lowercase
trim()
Remove white space on both sides ,IE8 This method is not supported in versions and below . Use replace It can also be implemented in combination with regularization , But it's relatively troublesome .

Summary reference ：https://www.w3school.com.cn/js/js_string_methods.asp