How to modify the value of a JavaScript map? - Stack Overflow

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My Javascript map object maps each key to an array. I have an issue with updating the array.

I tried to use a javascript object only.

const temp = {"map":[1], "what":[1,2]};
temp["what"].push(3);
console.log(temp);

It works but I still want to know whether there is a way to update the map object.

My original code is like this:

const temp = new Map();
temp.set("what", [1]);
temp["what"].push(2);
console.log(temp);

expect: {"what"=>[1,2]}

actual result:

VM6258:1 Uncaught TypeError: Cannot read property 'push' of undefined at <anonymous>:1:12

My Javascript map object maps each key to an array. I have an issue with updating the array.

I tried to use a javascript object only.

const temp = {"map":[1], "what":[1,2]};
temp["what"].push(3);
console.log(temp);

It works but I still want to know whether there is a way to update the map object.

My original code is like this:

const temp = new Map();
temp.set("what", [1]);
temp["what"].push(2);
console.log(temp);

expect: {"what"=>[1,2]}

actual result:

VM6258:1 Uncaught TypeError: Cannot read property 'push' of undefined at <anonymous>:1:12

• javascript

Share Improve this question Follow asked Dec 28, 2018 at 0:35 Lusha LiLusha Li 1,16822 gold badges1313 silver badges2525 bronze badges

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1 Answer 1

Sorted by: Reset to default 7

You need to use get with Map, i.e.

temp.get("what").push(2)

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