javascript 中的正则表达式：RegExp(exec, test) 和 String(match, search, replace, split)

var expression1 = /pattern /flags ;
var expression2 = new RegExp("pattern","flags");


var exp1 = /[bc]at/i;
var exp2 = new RegExp("[bc]at","i");   // 与exp1是等价的

    var text = "mom and dad and baby";
    var pattern = /mom( and dad( and baby)?)?/gi;
    
    var matches = pattern.exec(text);
    console.log(matches);// 0: "mom and dad and baby", 1: " and dad and baby", 2: " and baby", groups: undefined, index: 0, input: "mom and dad and baby", length: 3
    console.log(pattern.lastIndex); // 20

    matches = pattern.exec(text);
    console.log(matches);    //null
    console.log(pattern.lastIndex); // 0

    text = "vat ,bat, sat, fat";
    var pattern1 = /.at/;
    
    var matches = pattern1.exec(text);
    console.log(matches.index);  //0
    console.log(matches);  //0: "vat", groups: undefined, index: 0, input: "vat ,vat, sat, fat", length: 1
    console.log(pattern1.lastIndex); //0
    
    matches = pattern1.exec(text);
    console.log(matches.index);  //0
    console.log(matches);  //0: "vat", groups: undefined, index: 0, input: "vat ,vat, sat, fat", length: 1
    console.log(pattern1.lastIndex); //0
    
    var pattern2 = /.at/g;
    
    matches = pattern2.exec(text);
    console.log(matches.index);  //0
    console.log(matches);  //0: "vat", groups: undefined, index: 0, input: "vat ,vat, sat, fat", length: 1
    console.log(pattern1.lastIndex);  //0
    
    matches = pattern2.exec(text);
    console.log(matches.index);  //5
    console.log(matches);  //0: "bat", groups: undefined, index: 5, input: "vat ,vat, sat, fat", length: 1
    console.log(pattern1.lastIndex);  //0
    
    matches = pattern2.exec(text);
    console.log(matches.index);  //10
    console.log(matches);  //0: "sat", groups: undefined, index: 10, input: "vat ,vat, sat, fat", length: 1
    console.log(pattern1.lastIndex);  //0

var text = "000-00-000";
var pattern = /\d{3}-\d{2}-\d{3}/;
if(pattern.test(text)){    //true
    console.log("the pattern was matched!"); // 执行语句
}

var text = "mom and dad and baby";
var pattern = /mom( and dad( and baby)?)?/i;

var matches = text.match(pattern);
console.log(matches);// 0: "mom and dad and baby", 1: " and dad and baby", 2: " and baby", groups: undefined, index: 0, input: "mom and dad and baby", length: 3
console.log(pattern.lastIndex); // 20

var pattern = /mom( and dad( and baby)?)?/gi;
matches = text.match(pattern);
console.log(matches);// ["mom and dad and baby"]
console.log(pattern.lastIndex); // 0

text = "vat ,bat, sat, fat";
pattern = /.at/;

//与 pattern.exec(text) 相同
matches = text.match(pattern);
console.log(matches);  //0: "vat", groups: undefined, index: 0, input: "vat ,vat, sat, fat", length: 1
console.log(pattern.lastIndex); //0


//如果match的匹配规则具有全局g属性，那么match返回的匹配结果，便是一个包含所有匹配结果的纯数组
pattern = /.at/g;
matches = text.match(pattern);
console.log(matches);  //["vat", "bat", "sat", "fat"]
console.log(pattern.lastIndex); //0

var text = "vat ,bat, sat, fat";
var pattern = /at/;

var pos = text.search(pattern);
console.log(pos);  // 1

var text = "cat ,bat, sat, fat";
var pattern = "at";

var result = text.replace(pattern,"ond");
console.log(result);  // "cond ,bat, sat, fat"

pattern = /at/g;
result = text.replace(pattern,"ond"); 
console.log(result); //"cond ,bond, sond, fond"

var str = '世界上最遥远的距离 不是生与死的距离 而是我就站在你的面前 你却不知道我爱你。',
 st = ['死','爱','距离'],
 pattern = '',
 alt = '',
 str1= "";

for(var i=0;i<st.length;i++){

    pattern = new RegExp(st[i],'g');
    for(var j=0;j<st[i].length;j++){
        alt+='*';
    }

    str1 = str.replace(pattern,alt);
    alt = '';
}

console.log(str); //世界上最遥远的距离 不是生与死的距离 而是我就站在你的面前 你却不知道我爱你。
console.log(str1); //世界上最遥远的** 不是生与*的** 而是我就站在你的面前 你却不知道我*你。

function htmlEscape(text){
    return text.replace(/[<>"&]/g,function(match,index,input){
        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;

var str = '2016/10/29';
var pattern = /(\d+)(\/)/g;
var data = str.replace(pattern,function(result,$1,$2){
    return $1+'.';
});
console.log(data); //2016.10.29
console.log(str.replace(pattern,"$1.")); //2016.10.29
console.log(str.replace(/\//g,".")); //2016.10.29

var str = 'hellow world!';
console.log(str.split('')); //  ["h", "e", "l", "l", "o", "w", " ", "w", "o", "r", "l", "d", "!"]
console.log(str.split('',5)); // ["h", "e", "l", "l", "o"]
console.log(str.split(/o/g)); //  ["hell", "w w", "rld!"]