The pattern string matching method

1.match ()  () method is essentially the same as calling the RegExp exec.

 var text = "cat, bat, sat, fat";
    var pattern = /.at/;
    
    //与pattern.exec(text)相同
    var matches = text.match(pattern);
    console.log(matches.index);     //0
    console.log(matches.input);     
    console.log(matches[0]);        //"cat"
    console.log(pattern.lastIndex); //0

2.search ()  returns the index of the string matches the first item; -1 is not always find the scratch.

    var text = "cat, bat, sat, fat",
        pos = text.search(/at/);
    console.log(pos);               //1

3.replace ()  replacement string operation. It accepts two parameters.

a. If the first parameter is a string, then only replace the first substring. To replace all sub-strings, the only way is to provide a global flag.

var text = "cat, bat, sat, fat",
    result = text.replace("at", "ond");
console.log(result);    //"cond, bat, sat, fat"
    
result = text.replace(/at/g, "ond");
console.log(result);    //"cond, bond, sond, fond"

b. If the second parameter is a string, it may be added some special character sequences.

var text = "cat, bat, sat, fat";
result = text.replace(/(.at)/g, "word ($1)");
console.log(result);    

C. The second parameter may be a function.

• In the case of only one match, this function will be transmitted to three parameters: pattern matches, the position and pattern matches the original string in the string.
• In the case where the regular expression defines a plurality of capture groups, parameters passed to the function is still the pattern matches, the first match of a capturing group, second ......, but the last two argument is still the same.

function htmlEscape(text){
        return text.replace(/[<>"&]/g, function(match, pos, originalText){
            switch(match){
                case "<":
                    return "&lt;";
                case ">":
                    return "&gt;";
                case "&":
                    return "&amp;";
                case "\"":
                    return "&quot;";
            }
        })
    }

    console.log(htmlEscape("<p class=\"greeting\"> Hello world! </p>"));
    //&lt;p class=&quot;greeting&quot;&gt; Hello world! &lt;/p&gt;

4. split () This method can be based on the designated delimiter string into a plurality of sub-strings, and the results in an array. The separator can be a string, or may be a RegExp object.

    var colorText = "red, biue, green, yellow";
    var colors1 = colorText.split(",");
    var colors2 = colorText.split(",","2");
    var colors3 = colorText.split(/[^\,]+/);
    console.log(colors1);   //["red", " biue", " green", " yellow"]
    console.log(colors2);   //["red", " biue"]
    console.log(colors3);   //["", ",", ",", ",", ""]

/[^\,]+/  表示不是逗号的连续字符