<script>var arr=[1,2,‘a‘];arr.length=5;p(arr[3]); //undefinedarr.length=1;p(arr[1]); //undefined</script>

<script>var arr=[‘f‘,1,2,‘a‘,‘b‘,‘c‘];for(var k in arr){    p(arr[k]);}//for in有时无法保证枚举顺序for(var i=0;i<arr.length;i++){    p(arr[i]);}/*f12abc*///v 数组的值,key下标,ar数组对象arr.forEach(function(v,key,ar){    ar[key]=v+"_";})p(arr);//f_,1_,2_,a_,b_,c_p(Object.keys(arr));  //0,1,2,3,4,5p(Object.getOwnPropertyNames(arr));//0,1,2,3,4,5,lengthp(arr.__proto__==Array.prototype); //truep(Object.getOwnPropertyNames(Array));// length,name,arguments,caller,prototype,isArray,observe,unobserve</script>

<script>var arr=[‘f‘,1,2,‘a‘,‘b‘,‘c‘];p( arr.constructor);//function Array() { [native code] }p(Array.constructor);//function Function() { [native code] }p(Array.prototype.constructor);//function Array() { [native code] }p(arr.constructor==Array.prototype.constructor);//truevar arr=[‘f‘,1,2,‘a‘,‘b‘,‘c‘];var a=‘w‘;var arr1=[‘q‘,‘w1‘];var b=arr.concat(a,arr1);p(b);//f,1,2,a,b,c,w,q,w1var c=‘a‘.concat(‘b‘);p(c);//ab</script>

<script>var arr=[‘f1‘,1,2,‘a‘,‘b‘,‘c‘];function callback(element,index,arrobj){    return arrobj[index]=element+‘_‘;    //此函数必须return true默认return false,到return false就停止执行}arr.every(callback);  //truep(arr);//f1_,1_,2_,a_,b_,c_</script>

<script>var arr=[‘f1‘,1,2,‘a‘,‘b‘,‘c‘];function callback(element,index,arrobj){    if(!isNaN(element)) return true;}var arr1=arr.filter(callback);  //truep(arr1);//1,2</script>

<script>var arr=[‘f1‘,1,2,‘a‘,‘b‘,‘c‘,‘a‘];var r=arr.indexOf(‘a‘,3); //3  第二个参数不传的话默认从开始查找var r1=arr.indexOf(‘a‘,4);//6p(r,r1);//3,6p(‘abc‘.indexOf(‘c‘));//2</script>

<script>var arr=[‘f1‘,1,2,‘a‘,‘b‘,‘c‘,‘a‘];var str=arr.join(‘-‘);p(str);//f1-1-2-a-b-c-a</script>

<script>var arr=[‘f1‘,1,2,‘a‘,‘b‘,‘c‘,‘a‘,‘d‘];var r=arr.lastIndexOf(‘a‘,7);var r2=arr.lastIndexOf(‘a‘,3);p(r,r2);//6,3  找不到就返回-1</script>

<script>var arr=[‘f1‘,1,2,‘a‘,‘b‘,‘c‘,‘a‘,‘d‘];function callback(element,index,obj){    obj[index]=element+"__";    return element+"_";}var arr1=arr.map(callback);p(arr1);//f1_,1_,2_,a_,b_,c_,a_,d_p(arr);//f1__,1__,2__,a__,b__,c__,a__,d__</script>

<script>var arr=[‘f1‘,1,2,‘a‘,‘b‘,‘c‘,‘a‘,‘d‘];var arr1=arr.pop();//dp(arr,arr1);//f1,1,2,a,b,c,a       d</script>

<script>var arr1=[5,2,3,4,‘a‘];function callback(x,element){    p(x+":"+element);    return x+"_"+element;}var r=arr1.reduce(callback);p("<hr>");p(r);/*没初始值得结果5:25_2:35_2_3:45_2_3_4:a------------------------5_2_3_4_a有初始值得结果   r=arr1.reduce(callback,‘init‘);init:5init_5:2init_5_2:3init_5_2_3:4init_5_2_3_4:a-----------------------------------init_5_2_3_4_a*/</script>

<script>var arr=[‘f1‘,1,2,‘a‘,‘b‘,‘c‘,‘a‘,‘d‘];arr.reverse();p(arr);//d,a,c,b,a,2,1,f1</script>

<script>var arr=[‘f1‘,1,2,‘a‘,‘b‘,‘c‘,‘a‘,‘d‘];p(arr.shift());p(arr);</script>

<script>var arr=[‘f1‘,1,2,‘a‘,‘b‘,‘c‘,‘a‘,‘d‘];p(arr.unshift(‘first‘,‘second‘));//10p(arr);//first,second,f1,1,2,a,b,c,a,d</script>

<script>var arr=[‘f1‘,1,2,‘a‘,‘b‘,‘c‘,‘a‘,‘d‘];p(arr.slice(1,4));//1,2,ap(arr);//f1,1,2,a,b,c,a,d</script>

<script>var arr=[‘f1‘,1,2,‘a‘,‘b‘,‘c‘,‘a‘,‘d‘];p(arr.splice(1,2));//1,2p(arr);//f1,a,b,c,a,dvar arr=[‘f1‘,1,2,‘a‘,‘b‘,‘c‘,‘a‘,‘d‘];p(arr.splice(1,2,‘new‘,‘nn‘));//1,2p(arr);//f1,new,nn,a,b,c,a,d</script>

<script>var arr=[‘f1‘,1,2,‘a‘,‘b‘,‘c‘,‘a‘,‘d‘];function callbackfn(element,index,arrobj){    p(element+":"+index+":"+typeof arrobj);}arr.some(callbackfn);</script>

<script>ar arr=[‘f1‘,1,2,‘a‘,‘b‘,‘c‘,‘a‘,‘d‘];var r=arr.toLocaleString();var r1=arr.toString();p(r,r1);p(typeof r,typeof r1);</script>