Add property from one array with objects to another based on value

Question

I have two arrays of objects like this:

let test = [
{Course: "", Week: "1", Hours: ""}, 
{Course: "", Week: "2", Hours: ""}, 
{Course: "", Week: "3", Hours: ""}
]

let values = [{Course: "A", Week: "3", Hours: "1"}]

I want to add the property from array "values" to array "test so the result will be:

let test = [
{Course: "", Week: "1", Hours: ""}, 
{Course: "", Week: "2", Hours: ""}, 
{Course: "", Week: "3", Hours: "1"}
]

Is this possible? The reason why I have it like this, is I need to specify all weeks at the start, and the values will be added from the user.

Only a single property is changed so you can use test[2].Hours = values[0].Hours — Maheer Ali
– Maheer Ali, Commented Nov 30, 2020 at 18:52

Aplet123 · Accepted Answer · 2020-11-30 19:02:51Z

1

First make an object mapping weeks to objects for fast lookup then just loop through the values array:

const lookup = {};
for (const val of test) {
    lookup[val.week] = val;
}
for (const val of values) {
    const cur = lookup[val.week];
    for (const key in val) {
        if (key === "Hours") {
            cur[key] = (Number(cur[key]) + Number(val[key])).toString();
        } else {
            cur[key] = val[key];
        }
    }
}

edited Nov 30, 2020 at 19:02

answered Nov 30, 2020 at 18:53

Aplet123

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6 Comments

egx Over a year ago

Thank you! But if I have two values with the same week? E.g. let values = [{Course: "A", Week: "3", Hours: "1"}, {Course: "A", Week: "5", Hours: "1"}, {Course: "A", Week: "5", Hours: "1"}] Then it does not add them I guess

Aplet123 Over a year ago

If you have multiple values with the same week then what's your goal? Is it to overwrite both?

Moshe Sommers Over a year ago

@egx What's the expected behavior when two values have the same week?

egx Over a year ago

My goal would then to add the hours in the same value. So I would have {Course: "A", Week: "5", Hours: "2"} if I have to values of Week 5 with 1 Hour in them

egx Over a year ago

That would stay the same. So it only count the hours based on the weeks. The course actually is not that important, but rather the value of hours in weeks.

|

Moshe Sommers · Accepted Answer · 2020-11-30 18:56:20Z

0

Loop through Values - Find the test that matches current value's week and set hours to value's hours

values.forEach((value) => {
    //Find the test that matches current value's week and set hours to value's hours
    test.find(test => test.Week === val.Week).Hours = value.Hours);
});

answered Nov 30, 2020 at 18:56

Moshe Sommers

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Comments

devastro · Accepted Answer · 2020-11-30 18:58:43Z

0

You can just use array.find function.

let test = [
    {Course: "", Week: "1", Hours: ""}, 
    {Course: "", Week: "2", Hours: ""}, 
    {Course: "", Week: "3", Hours: ""}
]
    
let values = [{Course: "A", Week: "3", Hours: "1"}]

var current = test.find((item) => {
    return item.Week === values[0].Week
})
current.Hours += values[0].Hours;

console.log(test)

answered Nov 30, 2020 at 18:58

devastro

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