How to use a string as an object with diferent parameters in javascript?

Question

I have an array of post that is call test and the next code takes other array and push the post if the name equals something:

var test = [];
docs = [{name: 'mateo',lastName: 'mateo'},
        {name: 'Jhon',lastName: 'smith'}}]

docs.forEach(function(item) {
    if(item.name === 'mateo'){
        test.push(item);
    }
});

I want to use different parameters for the name, but I don´t know how, I was trying to use something like this but it did´t work:

var test = [];
docs = [{name: 'mateo', lastName: 'mateo'},
        {name: 'Jhon',lastName: 'smith'}}]
const varNames = ['name','lastName'];

docs.forEach(function(item) {
    for(i = 0; i < varNames.length; i++){
        if(item.[varNames[i]] === 'mateo'){
            test.push(item);
            console.log(varNames[i]);
        }
     } 
});

Please update your post to include a complete, runnable example. — Adam Chubbuck
– Adam Chubbuck, Commented Oct 14, 2018 at 23:25
If i use [varNames[i]] i get a syntax error when running nodejs ( I get an error with ["..."] too, I don´t know how to make that work is the problem. — Manuel Esteban
– Manuel Esteban, Commented Oct 14, 2018 at 23:27
@ManuelEsteban does test already have elements in it before forEach is called? — ibrahim mahrir
– ibrahim mahrir, Commented Oct 14, 2018 at 23:41

ibrahim mahrir · Accepted Answer · 2018-10-14 23:35:57Z

3

That's not how bracket notation work. Change

if(item.["varNames[i]"] === 'mateo') {

To:

if(item[varNames[i]] === 'mateo') {

By the way, you should break the loop once an item is matched:

if(item[varNames[i]] === 'mateo') {
    test.push(item);
    break;
}

You could also replace that whole for loop with another array function called some, so that your whole code looks like:

docs.forEach(function(item) {
    var check = varNames.some(function(varName) {
        return item[varName] === 'mateo';
    });
    if(check) {
        test.push(item);
    }
})

Which can be shorter if you use an arrow function:

docs.forEach(item => {
    if(varNames.some(varName => item[varName] === 'mateo')) {
        test.push(item);
    }
})

edited Oct 14, 2018 at 23:35

answered Oct 14, 2018 at 23:29

ibrahim mahrir

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2 Comments

Manuel Esteban Over a year ago

Thank you the some() method for arrays is the solution to my problem.

ibrahim mahrir Over a year ago

@ManuelEsteban You're welcome! BTW, the for loop works fine too, you just need to correct the syntax of the bracket notation and add the break statement.

Mark · Accepted Answer · 2018-10-14 23:38:23Z

2

You should really be using filter() for this, everything will be easier:

let docs = [
  {name: 'mateo', lastName: 'johnson'},
  {name: 'Jhon',lastName: 'smith'},
  {name: 'Mark',lastName: 'mateo'}
]

var test = docs.filter(item =>item.name === "mateo") 
console.log(test)

Then to check for an array of names you can simple use some() to see if some of the properties match:

let docs = [
  {name: 'mateo', lastName: 'johnson'},
  {name: 'Jhon',lastName: 'smith'},
  {name: 'Mark',lastName: 'mateo'}
]
const varNames = ['name','lastName'];

var test = docs.filter(item => varNames.some(name => item[name] == 'mateo'))

console.log(test)

edited Oct 14, 2018 at 23:38

answered Oct 14, 2018 at 23:33

Mark

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Comments

Darren · Accepted Answer · 2018-10-14 23:44:56Z

0

The trick is to iterate over both varNames and docs. You're familiar with .forEach, so this example uses it, though this may be a better case for .filter.

const test = [];
const varNames = ['name', 'otherName'];
const docs = [
  { name: 'mateo' },
  { name: 'name' },
  { name: 'otherName' }
];

varNames.forEach(varName => {
  docs.forEach(doc => {
    if (doc.name === varName) test.push(doc);
  });
});
console.log(test);

edited Oct 14, 2018 at 23:44

answered Oct 14, 2018 at 23:30

Darren

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