JS string built-in function

One 、 With special effects , The string will be labeled accordingly ：（ understand ）

1、big() <big> </big> label , Display strings in large font

2、anchor（）a label Create anchors , <a name="...."> </a>

3、link() a label Linked <a href="...."> </a>

<script>
    re=str.anchor("http://www.baidu.com")
	re=str.link("http://www.baidu.com")
</script>

4、bold() <b></b> Use bold to display strings

5、blink（） Highlighted Show flashing string

6、footcolor Use the specified color to display the string

7、footsize Use the specified size to display the string

<script>
    var str="hello, Three Gorges University "
    re=str.fontcolor("red")
	re=str.fontsize("30px")
</script>

8、italics Display the string in italics

9、small() Use small font size to display string

10、sub() Display the string as superscript

11、sup() Display a string as a subscript

12、fixed() Display strings in typewriter text

Two 、 Focus on mastering

1、toUpperCase() Capitalize letters

2、toLocaleLowerCase() Turn the letters into lowercase

Design a method to turn the initial letter into capital by yourself ：

<script>
    String.prototype.FirstUppserCase=function() { // Add this method to the prototype 
        ver re = this[0].toUpperCase()
        for(var i=1;i<this.length;i++){
            re +=this[i]
        }
        return re
    }
    // Use ：
    var str = 'asdfghh'
    var re = str.FirstUppserCase()
    console.log(re)'Asdfghh'
</script>

3、toString() Convert to string

4、valueOf() Returns the original value of the string object

5、indexOf(x,?y) Is to detect whether a string appears , And return the subscript , If there is no return -1;x For the string to query , the second y Is the starting position of the query , The default is zero .

usage ：

<script>
    // Query the number of occurrences of a character 
    String.prototype.count1=function(str) {
				var re=-1;
				var count=0
			    do{					
					re=this.indexOf(str,re+1)
					if(re!=-1){count++}
				}while(re!=-1)	
				return 	count					
			}			
			var str=" Text content "
			var re=str.count1(" The string to query ")
			console.log(re)// Number of occurrences 
</script>

3、 ... and 、 Must master

1、substr（start,num）start Where to start taking ,num Take a few ;start It could be negative , Stands for counting from back to front

<script>
            var str = "addlist"
			var re1 = str.substr(0,3)
			var re2 = str.substr(-3,3)
			console.log(re1,re2) //add ist
</script>

2、substring(start,?end) Left closed right away   from start The subscript begins to take , Take the subscript end The last one of （？ Parameters with question marks are optional ）

3、split(“ Separator ”) Division , Split the string into an array , Split into an array with the selected delimiter , If this character does not exist in the string , Then the whole string returned is in an array alone .

Specify ：

        <script>
            var str="helxxlo"
			var arr=str.split("l")
			console.log(arr)// Print  ["he","xx","o"]
            var arr1=str.split("s")
            console.log(arr1)// Print  ["helxxlo"]
        </script>

4、slice() And substring() be similar Get a string fragment

<script>
    	    var str="hello"
			var re1=str.substring(0,4)
			var re2=str.slice(0,4)
			console.log(re1,re2) //hell hell
</script>

Four 、 Written test exercise : Put the current web page url The parameter of is resolved to an object

<script>
var url='http://www.hqyj.com/index.html?user=karen&page=10&count=100'
            // Resolve to this format {user:"karen",page:"10",count:"100"}
			function  parseurl(str) {
              var querystring=str.split("?")[1]
				var arr=querystring.split("&")//["user=karen","page=10","count=100"]
				var obj={}
				for(var i=0;i<arr.length;i++){
					var arr2=arr[i].split("=")
					obj[arr2[0]]=arr2[1]
				}
				return obj
			}
			var obj=parseurl(url)
			console.log(obj)

</script>

5、 ... and 、 Add （ Packaging object ）

. Syntax is a kind of syntax sugar that refers to data The standard writing is obj[ ]

Why string basic data is not reference data , But it can go through . What methods to use ？

Because when the string basic data uses point syntax , There will be an implicit operation ;

Implicit operation : When all basic data is used as objects , Their point syntax will have one more implicit operation （ Implicitly wrapped as an object ）

Specify ：

<script>
    var str = "jack"
    str.age = 20
    // Implicit packaging operation 
    var str = new String("jack")
    str.age = 20
    console.log(str.age)// Print 20
</script>