Comparing JSON arrays for similar values in typescript

Question

I have 2 JSON object, one is an array of strings and the other is an array of objects. I would like to check if a value from the string array exists within the object array, and if it does, set a specific value in the object array.

i.e: Given the following object array

### Object Array before
[{
   name: 'ABCDE',
   value: 'abcde',
   checked: false
},
{
   name: 'FGHIJ',
   value: 'fghij',
   checked: false
},
{
   name: 'KLMNO'
   value: 'klmno'
   checked: false
}]

and given the following string array:

[ 'fghij', 'klmno' ]

the result should be the following:

### Object Array after
[{
   name: 'ABCDE',
   value: 'abcde',
   checked: false
},
{
   name: 'FGHIJ',
   value: 'fghij',
   checked: true
},
{
   name: 'KLMNO'
   value: 'klmno'
   checked: true
}]

The string array isn't one; that is an object array. Should it be ['fghij','klmno'] ? — Bruno Grieder
– Bruno Grieder, Commented Mar 1, 2017 at 13:02

Bruno Grieder · Accepted Answer · 2017-03-01 15:07:31Z

2

Something like

 arr.map( v => Object.assign(v, {checked: stringArray.indexOf(v.value) !== -1 }))

arr is the original array, stringArray contains ['fghij','klmno']

edit: Typescript Playground demonstrating it

If you do not want the original array to be modified change the assign call to Object.assign({}, v, {checked: stringArray.indexOf(v.value) !== -1 })

edited Mar 1, 2017 at 15:07

answered Mar 1, 2017 at 13:05

Bruno Grieder

30k10 gold badges73 silver badges104 bronze badges

Sign up to request clarification or add additional context in comments.

5 Comments

Taahir Hassem Over a year ago

It works partialy, returning the following: [ { "checked": false }, { "checked": true }, { "checked": true } ] - none of the other data was mapped.

Bruno Grieder Over a year ago

Are you targeting ES6? Object.assign is basically doing a shallow "merge" of two objects but is only available in ES6. If not you must get a polyfill

Bruno Grieder Over a year ago

The polyfill is there: developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/…

Bruno Grieder Over a year ago

I have set-up a Typescript playground so that you can see it running. See edit above

Taahir Hassem Over a year ago

Thanks, I had an extra parenthesis at the end which caused only checked to return

Tamas Hegedus · Accepted Answer · 2017-03-01 15:01:30Z

I would suggest to collect the values in an ES6 Set object for code clarity and performance reasons.

Basically you have two option here: modify the array in place, or copying it. Example for both:

const data = [{
    name: 'ABCDE',
    value: 'abcde',
    checked: false
}, {
    name: 'FGHIJ',
    value: 'fghij',
    checked: false
}, {
    name: 'KLMNO',
    value: 'klmno',
    checked: false
}];

const toCheck = [ 'fghij', 'klmno' ];


const toCheckSet = new Set(toCheck);

// copying the data
const newData = data.map(obj => ({
    name: obj.name,
    value: obj.value,
    checked: toCheckSet.has(obj.value)
}));
console.log(newData);

// altering in place:
data.forEach(obj => { obj.checked = toCheckSet.has(obj.value); })
console.log(data);

Collectives™ on Stack Overflow

Comparing JSON arrays for similar values in typescript

2 Answers 2

5 Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

5 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related