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JavaScript: Extract the first half of a string of even length

JavaScript Basic: Exercise-59 with Solution

Write a JavaScript program to extract the first half of a string of even length.

Pictorial Presentation:

JavaScript: Extract the first half of a string of even length

Sample Solution:

HTML Code:

<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width">
  <title>JavaScript program to  extract the first half of a string of even length.</title>
</head>
<body>

</body>
</html>

JavaScript Code:

function first_half (str) {
  if (str.length % 2 == 0) {
    return str.slice(0, str.length / 2);
  }
  return str;
}
console.log(first_half("Python"));  
console.log(first_half("JavaScript")); 
console.log(first_half("PHP"));

Sample Output:

Pyt
JavaS
PHP

Flowchart:

Flowchart: JavaScript - Extract the first half of a string of even length

ES6 Version:

function first_half (str) {
  if (str.length % 2 == 0) {
    return str.slice(0, str.length / 2);
  }
  return str;
}
console.log(first_half("Python"));  
console.log(first_half("JavaScript")); 
console.log(first_half("PHP"));

Visualize JavaScript code execution:

The following tool visualize what the computer is doing step-by-step as it executes the said program:

Live Demo:

See the Pen JavaScript - Extract the first half of a string of even length - basic-ex-59 by w3resource (@w3resource) on CodePen.


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Previous: Write a JavaScript program to create a new string of 4 copies of the last 3 characters of a given original string.
Next: Write a JavaScript program to create a new string without the first and last character of a given string.

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JavaScript: Tips of the Day

How to insert an item into an array at a specific index (JavaScript)?

What you want is the splice function on the native array object.

arr.splice(index, 0, item); will insert item into arr at the specified index (deleting 0 items first, that is, it's just an insert). In this example we will create an array and add an element to it into index 2:

var arr = [];
arr[0] = "Jani";
arr[1] = "Hege";
arr[2] = "Stale";
arr[3] = "Kai Jim";
arr[4] = "Borge";

console.log(arr.join());
arr.splice(2, 0, "Lene");
console.log(arr.join());

Ref: https://bit.ly/2BXbp04