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JavaScript: Initialize and fill an array with the specified values

JavaScript fundamental (ES6 Syntax): Exercise-213 with Solution

Write a JavaScript program to initialize and fill an array with the specified values.

  • Use Array.from() to create an array of the desired length, Array.prototype.fill() to fill it with the desired values.
  • Omit the last argument, val, to use a default value of 0.

Sample Solution:

JavaScript Code:

//#Source https://bit.ly/2neWfJ2 
const initializeArrayWithValues = (n, val = 0) => Array(n).fill(val);
console.log(initializeArrayWithValues(5, 2));
console.log(initializeArrayWithValues(4, 0));

Sample Output:

[2,2,2,2,2]
[0,0,0,0]

Pictorial Presentation:

JavaScript Fundamental: Initialize and fill an array with the specified values.
JavaScript Fundamental: Initialize and fill an array with the specified values.

Flowchart:

flowchart: Initialize and fill an array with the specified values.

Live Demo:

See the Pen javascript-basic-exercise-213-1 by w3resource (@w3resource) on CodePen.


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Next: Write a JavaScript program to Initializes an array containing the numbers in the specified range (in reverse) where start and end are inclusive with their common difference step.

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JavaScript: Tips of the Day

Checking if a key exists in a JavaScript object?

Checking for undefined-ness is not an accurate way of testing whether a key exists. What if the key exists but the value is actually undefined?

var obj = { key: undefined };
obj["key"] !== undefined // false, but the key exists!

You should instead use the in operator:

"key" in obj // true, regardless of the actual value

If you want to check if a key doesn't exist, remember to use parenthesis:

!("key" in obj) // true if "key" doesn't exist in object
!"key" in obj   // ERROR!  Equivalent to "false in obj"

Or, if you want to particularly test for properties of the object instance (and not inherited properties), use hasOwnProperty:

obj.hasOwnProperty("key") // true

Checking for undefined-ness is not an accurate way of testing whether a key exists. What if the key exists but the value is actually undefined? var obj = { key: undefined }; obj["key"] !== undefined // false, but the key exists! You should instead use the in operator: "key" in obj // true, regardless of the actual value If you want to check if a key doesn't exist, remember to use parenthesis: !("key" in obj) // true if "key" doesn't exist in object !"key" in obj // ERROR! Equivalent to "false in obj" Or, if you want to particularly test for properties of the object instance (and not inherited properties), use hasOwnProperty: obj.hasOwnProperty("key") // true For performance comparison between the methods that are in, hasOwnProperty and key is undefined.

Ref: https://bit.ly/2CFNp1X