20 commonly used string methods and their usage in JS (summary)

The following article will introduce you to 20 commonly used string methods and their usage in JavaScript. It has certain reference value. Friends in need can refer to it. I hope it will be helpful to you.

1. charAt(x)

charAt(x)Returns the character at position x in the string, with the subscript starting from 0 start.

    //charAt(x)
    var myString = 'jQuery FTW!!!';
    console.log(myString.charAt(7));
    //output: F

2. charCodeAt(x)

`charCodeAt(x)`返回字符串中`x`位置处字符的`unicode`值。

    //charAt(position)
    var message="jquery4u"
    //alert "113"
    alert(message.charAt(1)

3. concat(v1,v2..)

concat() method is used to connect two One or more strings, this method does not change the existing string and returns the new string after concatenation.

    //concat(v1, v2,..)
    var message="Sam"
    var final=message.concat(" is a"," hopeless romantic.")
    //alerts "Sam is a hopeless romantic."
    alert(final)

4. fromCharcode(c1,c2)

fromCharcode(c1,c2)Convert a set of Unicode values ​​into characters.

    //fromCharCode(c1, c2,...)
    console.log(String.fromCharCode(97,98,99,120,121,122))
    //output: abcxyz
    console.log(String.fromCharCode(72,69,76,76,79))
    //output: HELLO

5. indexOf(substr, [start])

indexOf method searches and (if found) returns the character or substring searched for in the string. index. If not found, -1 is returned. Start is an optional parameter that specifies the position in the string to start searching. The default value is 0.

    //indexOf(char/substring)
    var sentence="Hi, my name is Sam!"
    if (sentence.indexOf("Sam")!=-1)
    alert("Sam is in there!")

6. lastIndexOf(substr, [start])

lastIndexOf() method returns the index of the last occurrence of the specified text in the string, if not found, Then return -1. "Start" is an optional parameter that specifies the position in the string to start searching. The default value is string.length-1.

    //lastIndexOf(substr, [start])
    var myString = 'javascript rox';
    console.log(myString.lastIndexOf('r'));
    //output: 11

7. match(regexp)

Search for matches in a string based on a regular expression. If no match is found, an information array or null is returned.

    //match(regexp) //select integers only
    var intRegex = /[0-9 -()+]+$/;  
     
    var myNumber = '999';
    var myInt = myNumber.match(intRegex);
    console.log(isInt);
    //output: 999
     
    var myString = '999 JS Coders';
    var myInt = myString.match(intRegex);
    console.log(isInt);
    //output: null

8. replace(regexp/substr, replacetext)

replace() method is used to replace some characters with other characters in a string, or replace a A substring that matches the regular expression.

    //replace(substr, replacetext)
    var myString = '999 JavaScript Coders';
    console.log(myString.replace(/JavaScript/i, "jQuery"));
    //output: 999 jQuery Coders
     
    //replace(regexp, replacetext)
    var myString = '999 JavaScript Coders';
    console.log(myString.replace(new RegExp( "999", "gi" ), "The"));
    //output: The JavaScript Coders

9. search(regexp)

search() method is used to retrieve a specified substring in a string, or to retrieve a string that matches a regular expression Substring, if found, returns the starting position of the substring matching regexp, otherwise returns -1.

    //search(regexp)
    var intRegex = /[0-9 -()+]+$/;  
     
    var myNumber = '999';
    var isInt = myNumber.search(intRegex);
    console.log(isInt);
    //output: 0

10. slice(start, [end])

slice() method can extract a certain part of the string and return a new string. Includes all characters in the string starting at start (including start) and ending at end (excluding end).

    //slice(start, end)
    var text="excellent"
    text.slice(0,4) //returns "exce"
    text.slice(2,4) //returns "ce"

11. split(delimiter, [limit])

split() method is used to split a string into a string array and return a string array The strings in the returned array do not include delimiter itself. The optional "limit" is an integer that allows you to specify the maximum number of elements in the array to be returned.

12. substr(start, [length])

substr() method can extract the subscript starting from start in the string specified number of characters. Returns a new string containing length characters starting at start, including the character pointed to by start. If length is not specified, the returned string contains characters from start to the end of the string.

    //substring(from, to)
    var text="excellent"
    text.substring(0,4) //returns "exce"
    text.substring(2,4) //returns "ce"

13. substring(from, [to])

substring() method is used to extract the characters between two specified subscripts in the string. The substring returned by the method includes the characters at start, but does not include the characters at stop. to is optional. If this parameter is omitted, the returned substring The string will continue until the end of the string.

    //substring(from, [to])
    var myString = 'javascript rox';
    myString = myString.substring(0,10);
    console.log(myString)
    //output: javascript

14. toLowerCase()

toLowerCase() method is used to convert strings to lowercase.

    //toLowerCase()
    var myString = 'JAVASCRIPT ROX';
    myString = myString.toLowerCase();
    console.log(myString)
    //output: javascript rox

15. toUpperCase()

toUpperCase() method is used to convert strings to uppercase.

    //toUpperCase()
    var myString = 'javascript rox';
    myString = myString.toUpperCase();
    console.log(myString)
    //output: JAVASCRIPT ROX

16. includes()

includes() method is used to check whether a string contains a specified string or character.

    //includes()
    var mystring = "Hello, welcome to edureka";
    var n = mystring.includes("edureka");
    //output: True

17. endsWith()

endsWith()The function checks whether the string ends with the specified string or character.

    //endsWith()
    var mystr = "List of javascript functions";
    var n = mystr.endsWith("functions");
    //output: True

18. repeat()

repeat() Constructs and returns a new string containing the specified number of strings concatenated together. copy.

    //repeat()
    var string = "Welcome to Edureka";
    string.repeat(2);
    //output: Welcome to Edureka Welcome to Edureka

19. valueOf()

valueOf() method returns the primitive value of a String object, which is equivalent to String.prototype.toString().

    //valueOf()
    var mystr = "Hello World!";
    var res = mystr.valueOf();
    //output: Hello World!

20. trim()

trim() method removes whitespace characters from both ends of a string. Whitespace characters in this context are all whitespace characters (space, tab, no-break space, etc.) and all line terminator characters (such as LF, CR)

    //trim()
    var str = "     Hello Edureka!     ";
    alert(str.trim());

相关免费学习推荐：js视频教程

The above is the detailed content of 20 commonly used string methods and their usage in JS (summary). For more information, please follow other related articles on the PHP Chinese website!