var colors = new Array();//创建数组 
var count = colors.push("red","green");//推入两项 
console.log(count); 
 
var color = ["red","black"]; 
color.push("brown");//推入另一项 
color[3]="yellow"; //添加一项 
console.log(color); 
console.log(color.push("blue")); 
console.log(color.pop());//取得最后一项 

var colorArr = new Array();//创建数组 
colorArr.push("red","yellow");//推入两项 
console.log(colorArr); 
var length = colorArr.push("blue"); 
console.log(length); 
 
var item = colorArr.shift();//取得第一项 
console.log(item); 
console.log(colorArr.length); 

 function append(arr, item) { 
  var newArr = arr.slice(0); // slice(start, end)浅拷贝数组 
  newArr.push(item); 
  return newArr; 
}; 

 function append(arr, item) { 
  var length = arr.length, 
    newArr = []; 
  
  for (var i = 0; i < length; i++) { 
    newArr.push(arr[i]); 
  } 
  
  newArr.push(item); 
  
  return newArr; 
}; 

function append(arr, item) { 
  return arr.concat(item); 
} 

function insert(arr, item, index) { 
  var newArr=[]; 
  for(var i=0;i<arr.length;i++){ 
    newArr.push(arr[i]); 
  } 
  newArr.splice(index,0,item); 
  return newArr; 
} 

function insert(arr, item, index) { 
  var newArr=arr.slice(0); 
  newArr.splice(index,0,item); 
  return newArr; 
} 

function insert(arr, item, index) { 
  var newArr=arr.concat(); 
  newArr.splice(index,0,item); 
  return newArr; 
} 

function truncate(arr, item) { 
  var newArr=[]; 
  for(var i=0;i<arr.length-1;i++){ 
    newArr.push(arr[i]); 
  } 
  return newArr; 
} 

function truncate(arr) { 
  var newArr = arr.concat(); 
  newArr.pop(); 
  return newArr; 
} 

function curtail(arr) { 
  var newArr=[]; 
  for(var i=1;i<arr.length;i++){ 
    newArr.push(arr[i]); 
  } 
  return newArr; 
} 

function curtail(arr) { 
  var newArr = arr.concat(); 
  newArr.shift(); 
  return newArr; 
} 

function curtail(arr) { 
  return arr.slice(1); 
} 

function concat(arr1, arr2) { 
  var newArr=[]; 
  for(var i=0;i<arr1.length;i++){ 
    newArr.push(arr1[i]); 
  } 
  for(var j=0;j<arr2.length;j++){ 
    newArr.push(arr2[j]); 
  } 
  return newArr; 
} 

function concat(arr1, arr2) { 
  return arr1.concat(arr2); 
} 

function concat(arr1, arr2) { 
  var newArr=arr1.slice(0); 
  for(var i=0;i<arr2.length;i++){ 
    newArr.push(arr2[i]); 
  } 
  return newArr; 
} 

function remove(arr, item) { 
      var newArr = arr.slice(0); 
      for(var i=0; i<newArr.length; i++) { 
        if(newArr[i] == item) { 
          newArr.splice(i, 1); 
        } 
      } 
      return newArr; 
    } 
    var arr = [1,2,3,4,2]; 
    var item = 2; 
    console.log(remove(arr, item)); 
    console.log(arr); 

function remove(arr,item){ 
  var newarr = []; 
  for(var i=0;i<arr.length;i++){ 
    if(arr[i] != item){ 
      newarr.push(arr[i]); 
    } 
  } 
  return newarr; 
}