Push in typescript is appending the last modified object in a loop-CodePudding

I am trying to create an array out of a modified object but the Array<any>.push() method always appends the object that gets modified at the end of the loop. Here is sample code that I am trying to work with:

let data: any = JSON.parse('{"messages":[{"id":"1234"},{"id":"2345"},{"id":"3456"}]}');
let myObject:any;
let idMapping: any[] = [];
for(let index = 0; index < 1; index  ) {
    myObject = {DocID: "", index: index};
    for (let val of data.messages) {
        myObject.DocID = val.id;
        // console.log("After update: ", myObject); // this gives me the correct object
        idMapping.push(myObject);
    }
}
console.log(idMapping) // array with same identical values, infact the last modified value in for loop

This is giving me a list of same objects against what I expected it to be a list of objects having different DocID.

I am new to typescript and Nodejs, so any help would be appreciated.

CodePudding user response：

You modify and add the same object to the array over and over again!

Instead you should create a new object every iteration:

let data: any = JSON.parse('{"messages":[{"id":"1234"},{"id":"2345"},{"id":"3456"}]}');
let idMapping: any[] = [];
for(let index = 0; index < 1; index  ) {
   
    for (let val of data.messages) {
       let myObject = {DocID: "", index: index};
        myObject.DocID = val.id;
        // console.log("After update: ", myObject); // this gives me the correct object
        idMapping.push(myObject);
    }
}
console.log(idMapping)