Manipulating objects in array of objects

Question

I have this javascript objects:

var arr1 = [{id:'124',name:'qqq'}, 
           {id:'589',name:'www'}, 
           {id:'45',name:'eee'},
           {id:'567',name:'rrr'}]

var arr2 = [{id:'124',name:'ttt'}, 
           {id:'45',name:'yyy'}

I need to replace objects in arr1 with items from arr2 with same id.

Here how I achive the desired result:

arr1.map(obj => arr2.find(o => o.id === obj.id) || obj);

And here is the result:

var arr1 = [{id:'124',name:'ttt'}, 
           {id:'589',name:'em'}, 
           {id:'45',name:'yyy'},
           {id:'567',name:'eme'}];

But the problem that this solution:

arr1.map(obj => arr2.find(o => o.id === obj.id) || obj);

Don't work in IE browser.

How can I change the row above to get the desired result in IE and chrome browsers?

var arr1 = [{
    id: '124',
    name: 'qqq'
}, {
    id: '589',
    name: 'www'
}, {
    id: '45',
    name: 'eee'
}, {
    id: '567',
    name: 'rrr'
}];

var arr2 = [{
    id: '124',
    name: 'ttt'
}, {
    id: '45',
    name: 'yyy'
}];

var res = arr1.map(obj => arr2.find(o => o.id === obj.id) || obj);

console.log(res);

What version of IE? You are using find and arrow functions which are ES6 features... — elclanrs
– elclanrs, Commented Jun 18, 2016 at 16:19

charlietfl · Accepted Answer · 2016-06-18 16:18:00Z

1

If you want to use Array.prototype.find() you would need to use recommended polyfill for browsers that don't support it.

See MDN Array.protoype.find() polyfill

answered Jun 18, 2016 at 16:18

charlietfl

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Comments

topheman · Accepted Answer · 2016-06-18 16:29:17Z

0

If you don't want to use a polyfill, simply reduce the ids first then map.

var arr1 = [{id:'124',name:'qqq'}, 
           {id:'589',name:'www'}, 
           {id:'45',name:'eee'},
           {id:'567',name:'rrr'}]

var arr2 = [{id:'124',name:'ttt'}, 
           {id:'45',name:'yyy'}]

var byIds = arr2.reduce((acc, item) => {
    acc[item.id] = item;
    return acc;
}, {})

var replacedArr1 = arr1.map(item => byIds[item.id] || item);

answered Jun 18, 2016 at 16:29

topheman

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Comments

noppa · Accepted Answer · 2016-06-18 16:38:54Z

0

You have tagged lodash to this, so why not use lodash functions _ .find and _ .map instead of the native functions with limited browser support.

_.map(arr1, obj => _.find(arr2, o => o.id === obj.id) || obj);

To state the obvious, you also need to transpile the ES6 style arrow functions and what not to support older browsers.

answered Jun 18, 2016 at 16:38

noppa

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Abdelrahman M. Allam · Accepted Answer · 2016-06-18 16:47:22Z

0

Please, did you think of underscorejs you will find cross browser functions like find, filter and map

 int lastIndex = 0 
 var result = _.map(arr1 , function(num){ 
      if (arr1.id == arr2[lastIndex].id){
         return arr2[lastIndex++];
      }
      return arr1;
 });

answered Jun 18, 2016 at 16:47

Abdelrahman M. Allam

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Comments

Nina Scholz · Accepted Answer · 2016-06-18 16:49:12Z

You could iterate over arr2 and build an object as hash table and then iterate over arr1 for changing the elements.

var arr1 = [{ id: '124', name: 'qqq' }, { id: '589', name: 'www' }, { id: '45', name: 'eee' }, { id: '567', name: 'rrr' }],
    arr2 = [{ id: '124', name: 'ttt' }, { id: '45', name: 'yyy' }],
    hash = Object.create(null);

arr2.forEach(function (a) {
    this[a.id] = a;
}, hash);

arr1.forEach(function (a, i, aa) {
    if (this[a.id]) {
        aa[i] = this[a.id];
    }
}, hash);

console.log(arr1);

Or use a version with short circuit.

var arr1 = [{ id: '124', name: 'qqq' }, { id: '589', name: 'www' }, { id: '45', name: 'eee' }, { id: '567', name: 'rrr' }],
    arr2 = [{ id: '124', name: 'ttt' }, { id: '45', name: 'yyy' }],
    hash = Object.create(null);

hash.count = arr2.length;

arr2.forEach(function (a) {
    this[a.id] = a;
}, hash);

arr1.some(function (a, i, aa) {
    if (this[a.id]) {
        aa[i] = this[a.id];
        return !--this.count;
    }
}, hash);

console.log(arr1);

Williz · Accepted Answer · 2016-06-18 16:54:58Z

0

What I would do is use a for loop to loop through each item in the 2nd array. Then loop through the first array to see if the ID matches. If it does, set the name to the name from the second array.

var arr1 = [{id:'124',name:'qqq'}, 
       {id:'589',name:'www'}, 
       {id:'45',name:'eee'},
       {id:'567',name:'rrr'}];

var arr2 = [{id:'124',name:'ttt'}, 
       {id:'45',name:'yyy'}];

for (var i = 0; i < arr2.length; i++) {
    for (var j = 0; j < arr1.length; j++) {
        if (arr2[i].id === arr1[j].id) {
            arr1[j].name = arr2[i].name;
        }
    }   
}

here is a fiddle https://jsfiddle.net/k0grurx5/

edited Jun 18, 2016 at 16:54

answered Jun 18, 2016 at 16:46

Williz

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