通过键合并带下划线的数组

Question

I have 2 arrays :

[{id:1,name:"name"},{id:2,name:"name2"} ,{id:3,name:"name3"}]

[{id:1,date:"123"},{id:2,date:"456"}]

Array 1 should be updated only if the id is equal : So the array 1 will looks like

It should not create a new array . Only update the array 1 based on array 2

[{id:1,name:"name",date:"123"},{id:2,name:"name2",date:"456"} ,{id:3,name:"name3"}]

I managed to do that with for loop on array2 and inside the for filter like the following :

._filter(array1,function(item){
 If(item.id=array2.id)
    Do smth and update the array1.date
})

How do I doing that in he best way ? Using underscore.js

Answer 1

You can do it using native language like this:

 const arr1 = [{id:1,name:"name"},{id:2,name:"name2"} ,{id:3,name:"name3"}]; const arr2 = [{id:1,date:"123"},{id:2,date:"456"}]; arr1.forEach((ele) => { const match = arr2.find(item => ele.id === item.id) || {}; Object.assign(ele, match); }); console.log(arr1); 

Answer 2

You can do something like this:

Iterate over array1 and check if the id of each item exists in array2 by using the some() method.

 var arr1 = [{id:1,name:"name"},{id:2,name:"name2"} ,{id:3,name:"name3"}]; var arr2 = [{id:1,date:"123"},{id:2,date:"456"}]; var missing = []; arr1.forEach( (item1, i) => { var isExist = arr2.some(item2 => item2.id === item1.id) if(!isExist) { missing.push(i); } }) missing.forEach(item => { arr2.push(arr1[item]); }) console.log(arr2); 

reference for some()

Answer 3

Try this :

 var a = [{id:1,name:"name"},{id:2,name:"name2"} ,{id:3,name:"name3"}] ; var b = [{id:1,date:"123"},{id:2,date:"456"}] ; var i = 0, j = 0 ; while( i < a.length ) { j = 0 ; while( j < b.length) { if ( a[i].id === b[j].id ) Object.assign( a[i] , b[j] ); j++; } i++; } console.log(a) ; 

Answer 4

You can use forEach to iterate over the second array and use findIndex to get the matched element from first array. If the id matches then update the object in the first array

 let arr1 = [{ id: 1, name: "name" }, { id: 2, name: "name2" }, { id: 3, name: "name3" }] let arr2 = [{ id: 1, date: "123" }, { id: 2, date: "456" }] arr2.forEach(function(acc) { let findArry1Index = arr1.findIndex(function(item) { return item.id === acc.id; }); if (findArry1Index !== -1) { arr1[findArry1Index].date = acc.date; } }); console.log(arr1) 

Answer 5

var a = [{id:1,name:"name"},{id:2,name:"name2"} ,{id:3,name:"name3"}];

var b = [{id:1,date:"123"},{id:2,date:"456"}];

a = _.map(a, function(e) { return _.extend(e, _.findWhere(b, {id: e.id})); });

a results in:

0: {id: 1, name: "name", date: "123"}
1: {id: 2, name: "name2", date: "456"}
2: {id: 3, name: "name3"}

However, I guess this qualifies as "creating a new array"? Maybe it can serve as an inspiration though ¯\\_(ツ)_/¯

Answer 6

You can use underscore's indexBy function to index your second array by id , and then simply use Object.assign(...) to update your first array's elements with their corresponding match by performing a lookup in the indexed elements object.

 let arr1 = [{id:1, name:"name"}, {id:2, name:"name2"}, {id:3, name:"name3"}] let arr2 = [{id:1, date:"123"}, {id:2, date:"456"}] const arr2Groups = _.indexBy(arr2, e => e.id); arr1.forEach(e => Object.assign(e, arr2Groups[e.id] || {})); console.log(arr1); 

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