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JavaScript Get the index of an object by its property

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Given an object, the task is to get the object’s index from the array of objects of the given property name and property value using JavaScript. we’re going to discuss a few techniques.

Below are the following approaches:

Method 1: Using Array map() Method

This method creates a new array with the return value of calling a function for every array element. This method calls the provided function once for each element in an array, with maintaining the order. 

Syntax:

array.map(function(currentValue, index, arr), thisValue)

Parameters:

  • function(currentValue, index, arr): This parameter is required. It specifies a function to be run for each element in the array.
    • currentValue: This parameter is required. It specifies the value of the current element.
    • index: This parameter is optional. It specifies the array index of the current element.
    • arr: This parameter is optional. It specifies the array object to which the current element belongs.
  • thisValue: This parameter is optional. it specifies a value to be passed to the function to be used as its “this” value. If this parameter is empty, the value “undefined” will be passed.

Example: This example uses the JavaScript Array map() Method to get the object’s index with a given property.

Javascript




let arrayObj = [{
    prop_1: 'val',
    prop_2: 'val_12',
    prop_3: 'val_13'
}, {
    prop_1: 'val',
    prop_2: 'val_22',
    prop_3: 'val_23'
}];
 
function GFG_Fun() {
    let prop = 'prop_2';
    let val = 'val_22';
    console.log("Index of prop = "
        + prop + " val = " + val +
        " is = " +
        arrayObj.map(function (e) {
            return e.prop_2;
        }).indexOf(val));
}
 
GFG_Fun();


Output

Index of prop = prop_2 val = val_22 is = 1

Method 2: Using for loop

Using for loop we can iterate over the array of objects and check the given value of prop matches or not.

Example 1: This example searches for the attribute name and its value in the array and if it gets it, It returns the index of an object otherwise returns -1.

Javascript




let arrayObj = [{
    prop_1: 'val',
    prop_2: 'val_12',
    prop_3: 'val_13'
}, {
    prop_1: 'val',
    prop_2: 'val_22',
    prop_3: 'val_23'
}];
 
function fun_2(array, attr, value) {
    for (let i = 0; i < array.length; i += 1) {
        if (array[i][attr] === value) {
            return i;
        }
    }
    return -1;
}
 
function GFG_Fun() {
    let prop = 'prop_2';
    let val = 'val_22';
 
    console.log("Index of prop = '" +
        prop + "' val = '" + val + "' is = "
        + fun_2(arrayObj, prop, val));
}
 
GFG_Fun();


Output

Index of prop = 'prop_2' val = 'val_22' is = 1

Method 3: Using findIndex() Method

The Javascript Array.findIndex() method is used to return the first index of the element in a given array that satisfies the provided testing function (passed in by the user while calling). Otherwise, if no data is found then the value of -1 is returned.

Example: In this example, we have used findIndex() Method

Javascript




let arrayObj = [{
    prop_1: 'val',
    prop_2: 'val_12',
    prop_3: 'val_13'
}, {
    prop_1: 'val',
    prop_2: 'val_22',
    prop_3: 'val_23'
}];
 
const index = arrayObj.findIndex(object => {
    return object.prop_3 === 'val_23';
});
 
console.log(index);


Output

1

Method 4: Using some() Method

The Javascript arr.some() method checks whether at least one of the elements of the array satisfies the condition checked by the argument method. 

Example: In this example we have used some() Method

Javascript




let arrayObj = [{
    prop_1: 'val',
    prop_2: 'val_12',
    prop_3: 'val_13'
}, {
    prop_1: 'val',
    prop_2: 'val_22',
    prop_3: 'val_23'
}];
 
let index;
 
arrayObj.some((object, idx) => {
    if (object.prop_2 === 'val_12') {
        index = idx;
        return true;
    }
});
 
console.log(index);


Output

0


Last Updated : 09 Jan, 2024
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