Javascript简写条件语句(推荐)

经常在各处牛人的代码中看到许多简写的条件表达语句，看了一些介绍这方面的文章，觉得3 ways 2 say if这篇文章（http://www.thomasfrank.se/3_ways_2_say_if.html）还不错。在这篇文章中作者对传统的if...else...、?:、&&/||三种条件表达的写法的特点及用处进行了总结归纳，简述如下：

1. if...else结构

// Set r to 0 or 1 var r= Math.floor(2*Math.random())  // Set a, b and c to "small" if r==0 an else set them to "big" // using three different techniques  // Method 1: If else var a; if (r==0){a = "small"} else {a = "big"};  // Method 2: Conditional operator var b = r==0 ? "small" : "big";  // Method 3: And/or operators var c = r==0 && "small" || "big";  // Check the values of our variables alert(r+" "+a+" "+b+" "+c);

2. if...else if...else结构

// Set r to 0,1,2 or 3 var r= Math.floor(4*Math.random())  // Set a, b and c to "nada","small","big" and "huge" // depending on the value or r using three different techniques  // Method 1: If.. else if... else var a; if (r==0){a="nada"} else if (r==1){a="small"} else if (r==2){a="big"} else {a="huge"};  // Method 2: Conditional operators var b = r==0 ? "nada" : r==1 ? "small" : r==2 ? "big" : "huge";  // Method 3: And/or operators var c = r==0 && "nada" || r==1 && "small" || r==2 && "big" || "huge";  // Check the values of our variables alert(r+" "+a+" "+b+" "+c);

3. 执行函数

// Set r to 0,1,2 or 3 var r= Math.floor(4*Math.random())  // The global variable x and our four functions var x=""; nada=function(){x+="Nada! "}; small=function(){x+="Small! "}; big=function(){x+="Big! "}; huge=function(){x+="Huge! "};  // Call a specific function depending on the value of r // using three different techniques  // Method 1: If.. else if... else if (r==0){nada()} else if (r==1){small()} else if (r==2){big()} else {huge()};  // Method 2: Conditional operators r==0 ? nada() : r==1 ? small() : r==2 ? big() : huge();  // Method 3: And/or operators r==0 && (nada() || true) //nada()函数不一定返回true，为了保证后续的逻辑或||判断不被执行，需要返回true值，下同|| r==1 && (small() || true) || r==2 && (big() || true) || huge();  // Check the values of our variables alert(r+" "+x);

4. 执行代码

// Set r to 0,1,2 or 3 var r= Math.floor(4*Math.random())  // The global variable x var x="";  // Executing different code depending on the value of r // using three different techniques  // Method 1: If.. else if... else if (r==0){x+="Nada! "} else if (r==1){x+="Small! "} else if (r==2){x+="Big! "} else {x+="Huge! "};  // Method 2: Conditional operators r==0 ? function(){x+="Nada! "}() : r==1 ? function(){x+="Small! "}() : r==2 ? function(){x+="Big! "}() : function(){x+="Huge! "}();  // Method 3: And/or operators r==0 && (function(){x+="Nada! "}() || true) //有人在评论中指出这里的匿名函数是不必需的，在只有一条可执行代码时是这样的，但是如果有多条代码需要执行，匿名函数还是不错的|| r==1 && (function(){x+="Small! "}() || true) || r==2 && (function(){x+="Big! "}() || true) || function(){x+="Huge! "}();  // Check the values of our variables alert(r+" "+x);