I have an nested array. Example

let array = [['a','e1'],['b','b1']]

What i want to achive is a new nested array with a copy of one of the array's and a change to that copy.

when i run it though a loop (tried for and foreach) it duplicates the change throughout the entire nested array.

here is an example of the code (note its not key: index and just an example. the actual inside array contains 11 values in total)

let array = [['a','e1'],['b','b1']]

let result = []

for(let x of array){
    result.push(x);
    if(x[1]==='e1'){
        let newRow = x;
        newRow[1] = 'e2'
        result.push(newRow);
    }
}
//result: [[a,e2],[a,e2],[b,b1]]
let needResult = [['a','e1'],['a','e2'],['b','b1']]

Any assistance in this would be greatly appreciated.

Working example of the script : https://stackblitz.com/edit/js-ah1bvf?file=index.js

Thanks

CodePudding user response：

Instead of use let newRow = x;, as @tadman said in the comment you need to use another way like create a new array let newRow = []; //for example

let array = [['a','e1'],['b','b1'], ['c', 'e1']]

let result = []

for(let x of array){
    result.push(x);
    if(x[1]==='e1'){
        const newRow = [];
        newRow[0] = x[0];
        newRow[1] = 'e2'
        result.push(newRow);
    }
}
console.log(result)

CodePudding user response：

@tadman said in the comment let newRow = [...x] worked. I did not select @simons answer though valid as stated in my question the array can be quite large and i don't necessarily know exactly how long it is.

Thanks for the help!

CodePudding user response：

You have to deep copy that array try something like this

let newRow = JSON.parse(JSON.stringify(x))

So, your solution would be something like this

let array = [['a','e1'],['b','b1']]

let result = []

for(let x of array){
    result.push(x);
    if(x[1]==='e1'){
        let newRow = JSON.parse(JSON.stringify(x));
        newRow[1] = 'e2';
        result.push(newRow);
    }
}
console.log(result);

);