javascript map foreach

array items that meet certain criteria.3.map ()Map () is an array that runs the given function for each item in the array, returning the result of each function call. Each item of this array is the result of running an incoming function on the corresponding item in the original data, for example:var numbers=[1,2,3,4,5,4,3,2,1];var mapresult=numbers.map (function (Item,index,array) {return item*2;});alert (

List foreach Example Public classHelloWorld { Public Static voidMain (string[] args) {ListNewArraylist(); for(inti=1;i) {List.add (NewUser (i, "user_" +i)); } //List ForEachList.foreach (User-{User.setid (User.getid ()+ 10); SYSTEM.OUT.PRINTLN (user); }); } Private Static classuser{ PublicUser (Integer ID, String name) { This. ID =ID; This. Name =name; } Integer ID; String name; PublicInteger getId () {returnID; }

Recently, you need to store a data stored in the HashMap key and value to the database. The concrete structure is roughly mapinsert id= "Savematchresult" > INSERT into Sp4_acl_so (acl_id, so_uuid__proc_def_id) foreach collection= "Acldevicemap.keys" index= "index" item= "item" separator= "UNION All" > foreach collection= "acldevicemap[item" "Index=" Index_set "item=" set "separator=" UNION All "> SELEC

var array = [23,48,66,2]; ForEach: Loops, iterates through an array, no return value. Similar to For Loop Array.foreach (function (value, index, array) { console.log (value); return value * value;}); Map : The map means that the map returns a new array with a return value; Filterarr: Returns a new object var Maparr

. Map (FN) method var a=[2, 4, 6]; a.map(function(d, i, arr){ return {x:i, y:d*i, z:arr}; }); Output Result: [{x:0, y:0, z:[2, 4, 6]}, {x:1, y:4, z:[2, 4, 6]}, {x:2, y:12, z:[2, 4, 6]}] the D in the callback function is the value of the traversal array, and I is the index of the array, and the entire array is passed in the third parameter .map casts the origin

The newly added API interface forEach map filter in Array in ES5 some every indexOf lastIndexOf reduce reduceRight var array = [23,48,66,2]; ForEach: loop, traversing array; no return value. Similar to for Loop array.forEach(function( value, index, array ) { console.log(value); return value * value;} ); Map: in

vararr = [n/a];//[] is the new Array (All-in-one) syntax sugar (shorthand) varobj = {' name ': 2, ' Age ': 3};//{} is a shorthand for new Object () //var obj2 = new Object (); //obj2.name=2; //obj2.age=3; //ForEach facilitates all elements Arr.foreach (function(item,index) {//iterate over all elements of an arrayConsole.log (item)//1 2 3 })//Every determine if all elements meet all conditions varPD = Arr.every (function(item,index) {//used to determi

);//Index is 0index = Array.lastindexof (2,-2);//Index is 0index = Array.lastindexof (2,-1);//Index is 3//Results://[2, 5, 9, 2].lastindexof (2): 3//[2, 5, 9, 2].lastindexof (7):-1//[2, 5, 9, 2].lastindexof (2, 3): 3//[2, 5, 9, 2].lastindexof (2, 2): 0//[2, 5, 9, 2].lastindexof (2,-2): 0//[2, 5, 9, 2].lastindexof (2,-1): 3indexOf ():function as with LastIndexOf (), the search is in the forward direction // Find the element that meets the criteria: var array = [2, 5, 9]; var index = array.indexof

callback functionCharacteristicsThe map method invokes the callback function sequentially for each element in the original array . callback The return value (including undefined) after each execution is combined to form a new array. the callback function is only called on the indexed index, and those indexes that have never been assigned a value or deleted by using delete are not called. CaseAdd 2 to each item in the arrayvar arr = [' A ', ' B ', ' C

The 1.forEach method is used to invoke each element of an array and pass the element to a callback function.Array.foreach (function (Currentvalue,index,arr), thisvalue);1.currentValue must be. The current element.2.index is optional. The index value of the current element.3.arr is optional. The array object that corresponds to the current element4.thisValue is optional. The value passed to the function is generally used with this value, and if this ar

JS added several methods to the array in 1.6 for the map (), filter (), some (), every (), ForEach (), that is, there are so many methods.It is not clear that we are beginning to touch these, so we have a record here to deepen the impact. I mainly from two angles to understand and remember, one is the use of the API, one is the internal implementation.function briefMap (): Returns a new array with each elem

ES5 new Common Array methodLet arr = [1, 2, 3, 2, 1];A ForEach = to iterate over an arrayArr.foreach ((v, i) = = {Console.log (v, i);});Two map = Use an array to get a new array using a rule mapLet Maparr = Arr.map ((v, i) = = {Return v * v;});Arr.map ((v, i) = v * v); If there is only one sentence, you can omit the curly brace and returnConsole.log (Maparr); [1, 4, 9, 4, 1]Three filter = to find the elemen

JS added several methods to the array in 1.6 for the map (), filter (), some (), every (), ForEach (), that is, there are so many methods.It is not clear that we are beginning to touch these, so we have a record here to deepen the impact. I mainly from two angles to understand and remember, one is the use of the API, one is the internal implementation.function briefMap (): Returns a new array with each elem

specified function (callback), until this function returns false, and if this element is found, every returns falseif the callback function returns true after each element is executed. Every will return true. It executes the specified function only for non-empty elements in the array, no assignment, or the deleted element is ignoredTests whether all array elements are greater than or equal to 10:function Isbigenough (element, index, array) { ForEach