Ensure that immutability is strictly enforced, or allow for partial immutability without the risk of silently failing

Question

Ensure that immutability is strictly enforced, or allow for partial immutability without the risk of silently failing

Is there a method to implement partial immutability on an object in a way that triggers an error if any attempt at mutation is made?

For instance, consider let obj = {a: 1, b: 2}. I am interested in making obj.a and obj.b immutable while still allowing additional keys to be added to the object, such as obj.c = 3.

One approach I contemplated was nesting properties within sub-objects and utilizing Object.freeze like this:

let obj = {subObj:{a: 1, b:2}}; 
Object.freeze(obj.subObj);

However, it seems that subsequent changes fail silently. For example, obj.subObj.a = 3 does not alter a, nor does it raise any indication of an issue. Is there a way to ensure an error notification is triggered instead?

javascript ecmascript-6 immutability

Answer 1

Answer №1

A straightforward approach to handle this situation would be to use getters that return fixed values and setters that raise exceptions.

let obj = {
  get a() {
    return 1;
  },
  set a(val) {
    throw new Error('Can\'t set a');
  },
  get b() {
    return 2;
  },
  set b(val) {
    throw new Error('Can\'t set b');
  }
};
obj.c = 3; // works
console.log(obj);
obj.a = 4; // throws an error

Answer 2

A straightforward approach to handle this situation would be to use getters that return fixed values and setters that raise exceptions.

let obj = {
  get a() {
    return 1;
  },
  set a(val) {
    throw new Error('Can\'t set a');
  },
  get b() {
    return 2;
  },
  set b(val) {
    throw new Error('Can\'t set b');
  }
};
obj.c = 3; // works
console.log(obj);
obj.a = 4; // throws an error

Answer 3

Answer №2

Utilize Object.defineProperties() method and set the writable parameter to false for attributes "a" and "b", along with using "use strict" declaration and implementing try..catch..finally statements.

"use strict";

let example = new Object;

Object.defineProperties(example, {
  "a": {value:1, writable: false},
  "b": {value:2, writable: false}
});

try {
  example.c = 3;
  example.a = 3;
} catch (error) {
    console.log(error);
} finally {
    console.log(example);
}

Answer 4

Utilize Object.defineProperties() method and set the writable parameter to false for attributes "a" and "b", along with using "use strict" declaration and implementing try..catch..finally statements.

"use strict";

let example = new Object;

Object.defineProperties(example, {
  "a": {value:1, writable: false},
  "b": {value:2, writable: false}
});

try {
  example.c = 3;
  example.a = 3;
} catch (error) {
    console.log(error);
} finally {
    console.log(example);
}

Answer 5

Answer №3

One potential solution is to implement the use of strict mode.

Simply add the following line at the beginning of your file:

'use strict'

This will generate an exception if any modifications are attempted on a frozen object.

Answer 6

One potential solution is to implement the use of strict mode.

Simply add the following line at the beginning of your file:

'use strict'

This will generate an exception if any modifications are attempted on a frozen object.

Ensure that immutability is strictly enforced, or allow for partial immutability without the risk of silently failing

Answer №1

Answer №2

Answer №3

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