数组方法

数组方法

//isArray方法
    var months = ["January","Febraury","March","April","May","june","July","August","September","October","November","December"],
    items = {
        "0":"January",
        "1":"February",
        "2":"March",
        "3":"April",
        "4":"May"
    };
    console.log(Array.isArray(months)); //true
    console.log(Array.isArray(items)); //false
    
    
    //forEach方法
    months.forEach(function(value,index,fullArray){
        console.log(value + "is month number" + (index + 1) + "of" + fullArray.length);
    })
    //every和some方法
    var everyItemContainsR  = months.every(function(value,index,fullArray){
        return value.indexOf("r") >= 0;
    })
    //只有每一个都包含r才会返回true
    console.log(everyItemContainsR);//false
    var someItemContainsR = months.some(function(value,index,fullArray){
        return value.indexOf("r") >= 0;
    })
    //有一部分包含r就会返回true
    console.log(someItemContainsR);//true
    
    
    //map方法
    var daysOfTheWeek = ["Monday","Tuesday","Wednesday"],
    daysFirstLetters = daysOfTheWeek.map(function(value,index,fullArray){return value+"starts with"+value.charAt(0)});
    console.log(daysFirstLetters.join(", "));
    
    //filter方法
    monthsContainingR = months.filter(function(value,index,fullArray){
        return value.indexOf("r") >= 0;
    })
    console.log(monthsContainingR.join(", "));