By the end of this tutorial, you’ll use Lodash’s _.rangeRight() to build number arrays in reverse order—the mirror of _.range() with the same start, end, and step rules.
_.rangeRight(start, end, step)
As _.range.
High → low in array.
Walk arrays backward.
Use range + negative step.
Same as range.
_.rangeRight()?_.rangeRight() is the reversed sibling of _.range(). Lodash first computes the same progression—same start, end (exclusive), and step—then returns the numbers in opposite array order. It does not automatically count down from start to end unless that is what reversing _.range’s output produces.
_.rangeRight(10, 0) is [1, 2, …, 10], not [10, 9, …, 1]. For a literal countdown sequence, use _.range(10, 0, -1).
The classic use case is reverse iteration: _.rangeRight(array.length) yields indexes from last to first so you can walk an array backward without manual index math.
Identical signature to _.range():
_.rangeRight([start = 0], end, [step = 1 or -1])_.range(...).reverse() (Lodash implements this efficiently)._.rangeRight(5) → [4, 3, 2, 1, 0]._.range(start, end, -step), not rangeRight alone._.rangeRight(n) for indexes n-1 down to 0.import rangeRight from "lodash/rangeRight";
rangeRight(1, 5);
// [4, 3, 2, 1]| Task | Code pattern | Result |
|---|---|---|
| Reverse 0..n−1 | _.rangeRight(n) | [n−1 … 0] |
| Reverse 1..4 | _.rangeRight(1, 5) | [4, 3, 2, 1] |
| Step, reversed | _.rangeRight(1, 10, 2) | [9, 7, 5, 3, 1] |
| Reverse indexes | _.rangeRight(arr.length) | last → 0 |
| Countdown 10→1 | _.range(10, 0, -1) | Not rangeRight |
| Ascending order | _.range(...) | Low → high |
ArrayReversed nums
= rangeSame rules
High → lowIn array
UtilSequence
Same parameters as _.range()—only the output order differs:
start OptionalFirst value of the underlying progression. Defaults to 0 when only end is passed.
_.rangeRight(2, 5)end Required*Exclusive stop boundary—the end value is not in the result (before reversing).
_.rangeRight(1, 5)step OptionalStride between values in the underlying range; output is that sequence reversed.
_.rangeRight(0, 20, 5)return ArrayNumbers in reverse order of what _.range(same args) would return.
[4, 3, 2, 1]Mental model: _.rangeRight(a, b, c) ≈ _.range(a, b, c).reverse() for typical numeric inputs.
Practical _.rangeRight() patterns with copy-ready code, sample output, and interactive Try It Yourself labs.
Same math as range—numbers stored in reverse order.
_.range(1, 10, 2) is [1, 3, 5, 7, 9]; rangeRight flips it.
console.log(_.rangeRight(1, 10, 2));
console.log(_.range(1, 10, 2));
// [9, 7, 5, 3, 1]
// [1, 3, 5, 7, 9]Include 1 at the end—the old reference omitted it. Both arrays contain the same numeric set; only order differs.
Reverse of [1, 2, 3, 4].
console.log(_.rangeRight(1, 5));
console.log(_.rangeRight(0, 10, 3));
// [4, 3, 2, 1]
// [9, 6, 3, 0]End remains exclusive before the reverse—5 and 10 never appear.
Documented one-arg and signed-end cases.
console.log(_.rangeRight(4));
console.log(_.rangeRight(-4));
console.log(_.rangeRight(0, 20, 5));
console.log(_.rangeRight(0, -4, -1));
// [3, 2, 1, 0]
// [-3, -2, -1, 0]
// [15, 10, 5, 0]
// [-3, -2, -1, 0]Each line is the reverse of the matching _.range(...) call with the same arguments.
Reverse iteration and the countdown distinction.
The most common real-world use—reverse indexes without i-- loops.
const letters = ["a", "b", "c", "d", "e"];
_.rangeRight(letters.length).forEach((index) => {
console.log(letters[index]);
});
// e, d, c, b, a_.rangeRight(5) → [4, 3, 2, 1, 0]. Each index picks the next element from the end.
Do not use rangeRight for a 10→1 countdown—use negative step on range instead.
// Wrong tool for "10, 9, …, 1" display:
console.log(_.rangeRight(10, 0));
// [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
// Correct countdown sequence:
console.log(_.range(10, 0, -1));
// [10, 9, 8, 7, 6, 5, 4, 3, 2, 1]rangeRight reverses range’s output; range with -1 step builds descending values directly.
Side-by-side with range and native reverse.
Three ways to get related results—pick by intent.
const args = [2, 5];
console.log(_.rangeRight(...args));
console.log(_.range(...args).reverse());
console.log(_.range(...args));
// [4, 3, 2] — rangeRight
// [4, 3, 2] — manual reverse (same result)
// [2, 3, 4] — ascending rangePrefer rangeRight for clarity when you want reversed order; use range when ascending; use range + negative step for true descending values.
_.rangeRight() WorksSame rules as range—one arg becomes end, infer step sign from direction.
Compute the arithmetic sequence up to (but not including) end.
Return values from last generated to first—high index values appear first.
Same numbers as range, stored from end value toward start value.
_.rangeRight(10, 0) is [1…10]; _.range(10, 0, -1) is [10…1]._.range(...)._.rangeRight(arr.length) is cleaner than manual decrement loops._.rangeRight() is range with the result flipped—ideal for reverse indexes and any time you want the same numeric progression stored high-to-low. Remember the countdown pitfall: descending values usually mean _.range with a negative step.
When in doubt, log both _.range(...) and _.rangeRight(...) side by side—the relationship clicks immediately.
_.rangeRight(length) for reverse index iteration_.range(...).reverse()_.range(10, 0, -1) for literal countdown sequencesforEach or for…of for readable backward walks1 in step demos)_.rangeRight()Use these points when you need reversed numeric arrays.
Vs range.
CoreAs range.
SyntaxWalk arrays.
UsageUse range −step.
PitfallSame rule.
Rule_.rangeRight(2, 5) and _.range(2, 5).reverse() both yield [4, 3, 2]—rangeRight is essentially a convenience wrapper around the same progression logic with reversed output.
Try reversed step sequences, two-argument forms, and backward array iteration.
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