JavaScript: Get the first key that satisfies the provided testing function
JavaScript fundamental (ES6 Syntax): Exercise-236 with Solution
Write a JavaScript program to get the first key that satisfies the provided testing function. Otherwise return undefined.
- Use Object.keys(obj) to get all the properties of the object, Array.prototype.find() to test each key-value pair using fn.
- The callback receives three arguments - the value, the key and the object.
Sample Solution:
JavaScript Code:
//#Source https://bit.ly/2neWfJ2
const findKey = (obj, fn) => Object.keys(obj).find(key => fn(obj[key], key, obj));
console.log(findKey(
{
barney: { age: 36, active: true },
fred: { age: 40, active: false },
pebbles: { age: 1, active: true }
},
o => o['active']
));
Sample Output:
barney
Flowchart:

Live Demo:
See the Pen javascript-basic-exercise-236-1 by w3resource (@w3resource) on CodePen.
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Previous: Write a JavaScript program to get the last key that satisfies the provided testing function, otherwise undefined is returned.
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JavaScript: Tips of the Day
Hide DOM Elements Dynamically
DOM elements can be done dynamically using JavaScript.
We can use the stykle.display property to do it.
For instance, we can write :
element.style.display = 'none';
It's the same as setting display: 'none'.
If we want to toggle them element back on, we can write:
element.style.display = 'block'
Ref: https://bit.ly/3mp5NgH
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