Typescript class array assign by value

Question

How to assign typescript class object array by value not by reference. Below is the code

class Person {
    constructor(public Name: string, public Age: number) {
    }
}

let orignalArr: Person[] = [
    new Person('Gyan', 28),
    new Person('Parkash', 28),
];
let arr2 = orignalArr;    
//let arr2 = orignalArr.slice(0); i tried this but not working
arr2[0].Name = 'changed';
console.log(orignalArr);
//logs 0: Person {Name: "changed", Age: 28} 1: Person {Name: "Parkash", Age:
//  28}

console.log(arr2);
//logs 0: Person {Name: "changed", Age: 28} 1: Person {Name: "Parkash", Age:
//  28}

So what i need is the value of original array should not be changed.

Suren Srapyan · Accepted Answer · 2018-01-19 05:47:10Z

3

slice will not work, because your items are also reference type and it will just return the copies of the references.

You can use map function to iterate over array items and then using Object.assign, you can copy the properties of each object into the new object.

The example is provided in Javascript.

class Person {
    constructor(name, age) {
       this.name = name;
       this.age = age;
    }
}

let originalArr = [
    new Person('Gyan', 28),
    new Person('Parkash', 28),
];

let arr2 = originalArr.map(item => Object.assign({}, item));
arr2[0].name = 'Changed';

console.log(originalArr[0]);
console.log(arr2[0]);

answered Jan 19, 2018 at 5:47

Suren Srapyan

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2 Comments

Gyan Over a year ago

Thanks this is working, but i doubt it has impact on performance

Suren Srapyan Over a year ago

You will not notice that impact

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