Expansion and repair of strings in javascript framework design for reading notes_javascript skills

1.repeat method: Repeat a string n times. For example: repeat("chaojidan",2) -> chaojidanchaojidan

Method 1:

Copy code The code is as follows:

function repeat(str,n){
return Array.prototype.join.call({length:n 1},str);
//Execute the join method in the context of class array {length:n 1} and pass in str. That is, use str to separate the options of the class array. The class array is empty, so there are n str separated by n 1 "", and the result is n str connections.
}

Method 2:

Copy code The code is as follows:

function repeat(str,n){
var s = str ,total = "";
​while(n>0){                                                               //Assume n is 5, after n%2, it is equal to 1, so total = str.s=strstr. n=2. The second loop: s=strstrstrstr, n=1. The third loop total = strstrstrstrstr, break, jump out of the loop and return total, which happens to be the string where str is repeated 5 times
　　if(n%2 ==1){ 　　
　　 Total =s; //Here is 2 raised to the 0th power, which is 1. All positive integers can be combined using 1,2,4,8.... For example: 3=1 2,5=1 4,7=1 2 4.
　　}
　　if(n==1)　break;
​​ s =s; //What is used here is the power of 2, 2, 4, 8....
　　n = n>>1;
}
return total ;
}

2. Get the length of all bytes of the string: str.charCodeAt(i) >255. Just add the length of str once and it will be OK.

3. Convert camel case style: str.replace(/[-_][^-_]/g,function(match){return match.charAt(1).toUpperCase();})

//-_In [], there is no need to use it, and ^ in [] means the opposite, that is, when -a or _a is encountered, it will be replaced by A (match is a regular matching string _a, then take a and capitalize it)

4. Convert to underline style: str.replace(/([a-zd])([A-Z])/g,'$1_$2').replace(/-/g,'_').toLowerCase ();

//The first replace matches the string of cA or 4A, and then replaces it with c_A or 4_A. $1 represents the first subexpression. The second replacement is to use _ to replace -. Since - is not in [], it needs to be added.

5. Remove the html tag in the string: str.replace(/] >/g,''), which will remove the script tag, but will not remove the js script in the script.

6. Remove the script tag and remove the js script inside: str.replace(/<script>]*>(Ss)*?)</script>/img,'')

/ Need to be used to prevent escaping.

//(Ss)*?) Match as little as possible, non-greedy matching. For example: <script>aaa</script>dddd<script>bbbb</script> will match <script>aaa</script> first, then <script>bbbb</script>, if not Adding ? will be a greedy match, and will match all <script>aaa</script>dddd<script>bbbb</script>, even the string dddd will be removed.

7. Escape the string through html to obtain content suitable for display on the page.

str.replace(/&/g,'&').replace(/,'/g,'>').replace(/"/ g,'"').replace(/'/g,''');

8. Replace the html entity characters of the string with corresponding characters:

The opposite of 7, just one more replace(/([d] );/g,function($0,$1){ return String.fromCharCode(parseInt($1,10)) }) //$1 is The first subexpression match.

9.trim:str.replace(/^s | s $/g,'') , IE or early standard browsers do not list many blank characters as s, so there will be bugs. However, why insist on being compatible with obsolete browsers?