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JavaScript: Check whether an object contains specified property

JavaScript Object: Exercise-17 with Solution

Write a JavaScript function to check whether an object contains given property.

Sample Solution: -

HTML Code:

<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <title>JavaScript function to check whether an object contains given property.</title>
</head>
<body>

</body>
</html>

JavaScript Code:

function hasKey(obj, key) {
    return obj != null && hasOwnProperty.call(obj, key);
  }
console.log(hasKey({red: "#FF0000", green: "#00FF00", white: "#FFFFFF"}, "green"));

Sample Output:

true

Flowchart:

Flowchart: JavaScript:- Check whether an object contains given property

Live Demo:

See the Pen javascript-object-exercise-17 by w3resource (@w3resource) on CodePen.


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JavaScript: Tips of the Day

instance

class Calc {
	constructor() {
		this.count = 0 
	}

	increase() {
		this.count ++
	}
}

const calc = new Calc()
new Calc().increase()

console.log(calc.count)

We set the variable calc equal to a new instance of the Calc class. Then, we instantiate a new instance of Calc, and invoke the increase method on this instance. Since the count property is within the constructor of the Calc class, the count property is not shared on the prototype of Calc. This means that the value of count has not been updated for the instance calc points to, count is still 0.

Ref: https://bit.ly/2Hcpkm6