dojo 学习日记 之 数组操作
dojo 学习日记 之 数组操作
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dojo 对Javascript1.6 的数组操作功能进行了拓展：
- clearCache()
- every(arr, callback, thisObject) Determines whether or not every item in arr satisfies the condition implemented by callback.
- filter(arr, callback, thisObject) Returns a new Array with those items from arr that match the condition implemented by callback.
- forEach(arr, callback, thisObject) for every item in arr, callback is invoked.
- indexOf(arr, value, fromIndex, findLast) locates the first index of the provided value in the passed array.
- lastIndexOf(arr, value, fromIndex) locates the last index of the provided value in the passed array.
- map(arr, callback, thisObject, Ctr) applies callback to each element of arr and returns an Array with the results
- some(arr, callback, thisObject) Determines whether or not any item in arr satisfies the condition implemented by callback.
1.every(arr,callback,thisObject); 校验是否数组arr内的所有元素都满足回调函数的条件，是返回true
Parameter | Type | Description |
|---|---|---|
arr | Array | String | 用来迭代的数组. 如果是string，则对string的没资格字符操作 |
callback | Function | String | 回调函数被触发，三个参数: item, index, and array ，如果条件满足，返回为true |
thisObject | Object | 可选 可能作为回调函数的作用域 |
// returns false
array.every([1, 2, 3, 4], function(item){ return item>1; });
// returns true
array.every([1, 2, 3, 4], function(item){ return item>0; });2.filter(arr, callback, thisObject) ; 返回一个满足过滤条件元素组成的数组
Parameter | Type | Description |
|---|---|---|
arr | Array | the array to iterate over. |
callback | Function | String | a function that is invoked with three arguments (item, index, array). The return of this function is expected to be a boolean which determines whether the passed-in item will be included in the returned array. |
thisObject | Object | Optional may be used to scope the call to callback |
// Example
// returns [2, 3, 4]
array.filter([1, 2, 3, 4], function(item){ return item>1; });3.forEach(arr, callback, thisObject) 对arr 的每一个元素，触发回调函数
// log out all members of the array:
array.forEach(
[ "thinger", "blah", "howdy", 10 ],
function(item){
console.log(item);
}
);
// log out the members and their indexes
array.forEach(
[ "thinger", "blah", "howdy", 10 ],
function(item, idx, arr){
console.log(item, "at index:", idx);
}
);
// use a scoped object member as the callback
var obj = {
prefix: "logged via obj.callback:",
callback: function(item){
console.log(this.prefix, item);
}
};
// specifying the scope function executes the callback in that scope
array.forEach(
[ "thinger", "blah", "howdy", 10 ],
obj.callback,
obj
);
// alternately, we can accomplish the same thing with lang.hitch()
array.forEach(
[ "thinger", "blah", "howdy", 10 ],
lang.hitch(obj, "callback")
);4.indexOf(arr, value, fromIndex, findLast) 从fromIndex 起，返回arr数组中第一次出现value的索引值.
Parameter | Type | Description |
|---|---|---|
arr | Array | |
value | Object | |
fromIndex | Integer | Optional |
findLast | Boolean | Optional Makes indexOf() work like lastIndexOf(). Used internally; not meant for external usage. |
5.map(arr, callback, thisObject, Ctr) 根据回调函数映射数组值
Parameter | Type | Description |
|---|---|---|
arr | Array | String | the array to iterate on. If a string, operates on individual characters. |
callback | Function | String | a function is invoked with three arguments, (item, index, array), and returns a value |
thisObject | Object | Optional may be used to scope the call to callback |
Ctr | undefined | |
// returns [2, 3, 4, 5]
array.map([1, 2, 3, 4], function(item){ return item+1 });6.some(arr, callback, thisObject) 检验数组里是否有满足回调函数条件，有则返回true
Parameter | Type | Description |
|---|---|---|
arr | Array | String | the array to iterate over. If a string, operates on individual characters. |
callback | Function | String | a function is invoked with three arguments: item, index, and array and returns true if the condition is met. |
thisObject | Object | Optional may be used to scope the call to callback |
// is true
array.some([1, 2, 3, 4], function(item){ return item>1; });
// is false
array.some([1, 2, 3, 4], function(item){ return item<1; });