How Can JavaScript Generate Numeric and Character Ranges Without a Dedicated `range()` Function?

JavaScript's Built-In Capabilities for Generating Ranges

In PHP, the range() function is used to generate an array of values within specified bounds. JavaScript doesn't have a direct equivalent, but native methods can be employed to achieve similar functionality.

Numeric Ranges

To create a range of numbers, you can use the following technique:

[...Array(5).keys()]; // [0, 1, 2, 3, 4]

This code generates an array of values from 0 to 4 (inclusive).

Character Ranges

For a range of characters, use the following approach:

String.fromCharCode(...[...Array('D'.charCodeAt(0) - 'A'.charCodeAt(0) + 1).keys()].map(i => i + 'A'.charCodeAt(0))); // "ABCD"

This code generates the characters "A" to "D".

Iterated Ranges

Alternatively, you can use iteration to generate ranges:

for (const x of Array(5).keys()) {
  console.log(x, String.fromCharCode('A'.charCodeAt(0) + x));
} // 0,"A" 1,"B" 2,"C" 3,"D" 4,"E"

This code iterates over the numbers from 0 to 4 and prints the corresponding characters.

Creating Range Functions

To create reusable range functions, you can do the following:

function range(size, startAt = 0) {
    return [...Array(size).keys()].map(i => i + startAt);
}

function characterRange(startChar, endChar) {
    return String.fromCharCode(...range(endChar.charCodeAt(0) -
            startChar.charCodeAt(0), startChar.charCodeAt(0)))
}

Third-Party Libraries

The lodash.js library provides a _.range() function that simplifies range generation:

_.range(10); // [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

Legacy Browser Compatibility

For older browsers that don't support ES6, use the following code:

Array.apply(null, Array(5)).map(function (_, i) {return i;}); // [0, 1, 2, 3, 4]

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