Push an item to array of array in javascript

Question

Hi I am having an array like below and trying to push the item on map, but i am not able to push, Please tell what wrong i am doing here.

firstClassPrices: [
 [
 "Kan ej ombokas",
 "431",
 "SEK",
 "Företagspris"
 ],
 [
 "Kan ombokas",
 "525",
 "SEK",
 "Företagspris"
 ]
]

trying to push '1' like below:

 let ticketi = firstClassPrices.map((price) => {
 price.push("1");
 });

i need o/p as

firstClassPrices: [
 [
 "Kan ej ombokas",
 "431",
 "SEK",
 "Företagspris",
 "1"
 ],
 [
 "Kan ombokas",
 "525",
 "SEK",
 "Företagspris",
 "1"
 ]
 ]

• Ivar: Your code already works. You're only using .map() while not returning any elements from its callback function so the return value (which you store in ticketi will only contain undefined values. But the original firstClassPrices will contain what you are looking for.
• Sudhir: if "1" is already there in array how to skip the push

Answer 1

You have to return the price

const firstClassPrices = [
 [
 "Kan ej ombokas",
 "431",
 "SEK",
 "Företagspris"
 ],
 [
 "Kan ombokas",
 "525",
 "SEK",
 "Företagspris"
 ]
];
 let ticketi = firstClassPrices.map((price) => {
 // skip if price already includes 1
 if (!price.includes("1")) {
 price.push("1");
 }
 return price;
 });
console.log(ticketi);

• Ivar: In this code, both firstClassPrices and ticketi reference the same nested arrays. There is little added value in using .map() if you are going to modify the original array also.
• Sudhir: if "1" is already there in array how to skip the push
• callback: @Sudhir I updated the code with this requirement.

Answer 2

Your approach mutates the old array and maps undefined.

---

Instead, you could map the old and new content of the array.

This approach does not mutate the old data.

let ticketi = firstClassPrices.map(price => [...price, '1']); 

• Yosvel Quintero: Notice that according to OP: 1 should be of type string

Answer 3

You can use Array.prototype.map() combined with Array.prototype.concat()

Code:

const firstClassPrices = [["Kan ej ombokas","431","SEK","Företagspris"],["Kan ombokas","525","SEK","Företagspris"]]
const ticketi = firstClassPrices.map(p => p.concat('1'))
console.log(ticketi)

Answer 4

Since you want to mutate the original arrays, you can use the function Array.prototype.forEach.

The problem you're facing is regarding the missing return value inside of the map's handler, so basically, the handler is returning undefined

const array = [ [ "Kan ej ombokas", "431", "SEK", "Företagspris" ], [ "Kan ombokas", "525", "SEK", "Företagspris" ]],
 handler = (a) => a.push("1");
array.forEach(handler);
console.log(array);

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