What is the best way to retrieve a default property from a JavaScript literal object?

Question

What is the best way to retrieve a default property from a JavaScript literal object?

In the following example, a JS object is created:

var obj = {
      key1 : {on:'value1', off:'value2'},
      key2 : {on:'value3', off:'value4'}
}

Is there a clever method to automatically retrieve the default value of the key1 on property when only obj.key1 is passed without specifying a property?

var key1State = obj.key1; // I want 'value1' to be returned here instead of obj.key1{...}

Is it feasible to somehow determine within the body of the object definition which property (if any) is being requested when calling the object?

javascript properties object-literal

Answer 1

Answer №1

Perhaps this solution could be what you are searching for - by tinkering with the valueOf or toString methods.

Consider the following scenario:

let object = {
      property1 : {on:'data1', off:'data2', toString : function(){ return this.on; }},
      property2 : {on:'data3', off:'data4', toString : function(){ return this.on; }}
}

let stateOfProperty1 = object.property1; // returns the object
let stringStateOfProperty1 = '' + object.property1; // outputs "data1"
object.property1 == "data1"  // evaluates to true
object.property1.toString() === "data1"  // also true

Thus, in cases where using the default value as a string is necessary, this method could prove beneficial.

Answer 2

Perhaps this solution could be what you are searching for - by tinkering with the valueOf or toString methods.

Consider the following scenario:

let object = {
      property1 : {on:'data1', off:'data2', toString : function(){ return this.on; }},
      property2 : {on:'data3', off:'data4', toString : function(){ return this.on; }}
}

let stateOfProperty1 = object.property1; // returns the object
let stringStateOfProperty1 = '' + object.property1; // outputs "data1"
object.property1 == "data1"  // evaluates to true
object.property1.toString() === "data1"  // also true

Thus, in cases where using the default value as a string is necessary, this method could prove beneficial.

Answer 3

Answer №2

Although this solution may not directly address your issue, it could still prove to be helpful.

Consider utilizing getters in your code.

var data = {

  fruit : {ripe:'apple', unripe:'banana'},
  vegetable: {ripe:'tomato', unripe:'cucumber'}, 
  get selectedFood () { return this.fruit.ripe }

}

By implementing getters like this, you can easily access the desired values from your objects.

Answer 4

Although this solution may not directly address your issue, it could still prove to be helpful.

Consider utilizing getters in your code.

var data = {

  fruit : {ripe:'apple', unripe:'banana'},
  vegetable: {ripe:'tomato', unripe:'cucumber'}, 
  get selectedFood () { return this.fruit.ripe }

}

By implementing getters like this, you can easily access the desired values from your objects.

Answer 5

Answer №3

I understand your concept, but I believe the more efficient approach would be to utilize a function such as getState to retrieve the current state of the object.

var obj = {
  key1: {on:'value1', off:'value2'},
  key2: {on:'value3', off:'value4'}
};

var key1State = getState(obj.key1);
var key2State = getState(obj.key2.off);

function getState(obj) {
  return obj.on || obj;
}

console.log(key1State, key2State);

View codepen example.

Answer 6

I understand your concept, but I believe the more efficient approach would be to utilize a function such as getState to retrieve the current state of the object.

var obj = {
  key1: {on:'value1', off:'value2'},
  key2: {on:'value3', off:'value4'}
};

var key1State = getState(obj.key1);
var key2State = getState(obj.key2.off);

function getState(obj) {
  return obj.on || obj;
}

console.log(key1State, key2State);

View codepen example.

What is the best way to retrieve a default property from a JavaScript literal object?

Answer №1

Answer №2

Answer №3

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