关于优化的方式

摘自:http://www.cnblogs.com/lranye/archive/2013/06/08/3127013.html

3、当进行多个条件判段时

给一个例子：每种颜色对应一个值,比如"white","red","green","yellow","gray","blue" 分别对应的值为0,1,2,3,4,5

1) 问题一:根据值获取颜色

实现方式一

function getColorByVal(val) {
    var color = "";
    if (val == 0){
        color = "white";
    }else if (val == 1) {
        color = "red";
    } else if (val == 2) {
        color = "green";
    } else if (val == 3) {
        color = "yellow";
    } else if (val == 4) {
        color = "gray";
    } else if (val == 5) {
        color = "blue";
    } 
    return color;
}

实现方式二

function getColorByVal(val) {
    var color;
    switch (val) {
        case 0:
            color = "white";
        case 1:
            color = "red";
            break;
        case 2:
            color = "green";
            break;
        case 3:
            color = "yellow";
            break;
        case 4:
            color = "gray";
            break;
        case 5:
            color = "blue";
            break;
             
    }
    return color;
}

实现方式三

function getColorByVal(val) {
   return ["white","red","green","yellow","gray","blue"][val];
}

调用: var color=getColorByVal(2);

方式一和方式二相比没什么差别，但方式二稍微好一点，而方式三则是让人眼前一亮，短小精悍就完成了功能。不过有的人会说颜色的值刚好是数组

再有:

function getValByColor(color){
    return {"white":0,"red":1,"green":2,"yellow":3,"gray":4,"blue":5}[color];
}

调用: var val=getValByColor("red");