Range

Control Flow Primitives for displaying a number range or given number of elements.

• repeat - Primitive for mapping a number of elements. Underlying helper for the <Repeat> control flow.
• <Repeat> - Control Flow Component for displaying a number of elements.
• mapRange - Primitive for mapping a number range of given start, end, and step values. Underlying helper for the <Range> control flow.
• <Range> - Control Flow Component for displaying a number range of elements.
• indexRange - Primitive for mapping a number range while keeping previous elements of the same index. Underlying helper for the <IndexRange> control flow.
• <IndexRange> - Control Flow Component for displaying a number range of elements, where elements receive a number value as signal.

#repeat

Reactively maps a number range of specified length with a callback function - underlying helper for the <Repeat> control flow.

const [length, setLength] = createSignal(10)
const mapped = repeat(length, index => {
   const [value, setValue] = createSignal(index);
   createEffect(() => {...})
   return value
})

#Definition

function repeat<T>(
  times: Accessor<number>,
  mapFn: (i: number) => T,
  options?: {
    fallback?: Accessor<T>;
  },
): Accessor<T[]>;

#<Repeat>

Control Flow component for displaying a specified number of elements.

The times prop is reactive – changing it will only create new elements for added numbers.

<Repeat times={10}>
   <div></div>
</Repeat>

// with a render prop:
<Repeat times={10}>
   {n => <div>{n}</div>}
</Repeat>

// with fallback:
<Repeat times={0} fallback={<p>no items...</p>}>
   <div></div>
</Repeat>

#Definition

function Repeat<T>(props: {
  times: number;
  fallback?: T;
  children: ((index: number) => T) | T;
}): Accessor<T[]>;

#mapRange

Reactively maps a number range of specified stop, to and step, with a callback function - underlying helper for the <Range> control flow.

All stop, to and step arguments are accessors, and changing them will cause the mapped array to be recalculated, mapping new items for numbers added to the range.

step will become negative (the range will be descending) if to is smaller than start. Range stops at to, it is not included in the range.

const [to, setTo] = createSignal(5)
const mapped = mapRange(() => 0, to, () => 0.5, number => {
   const [value, setValue] = createSignal(number);
   createEffect(() => {...})
   return value
})
mapped() // => [0, 0.5, 1, 1.5, 2...]
setTo(3) // changes the output array, mapping only added numbers

#Definition

function mapRange<T>(
  start: Accessor<number>,
  to: Accessor<number>,
  step: Accessor<number>,
  mapFn: (n: number) => T,
  options?: {
    fallback?: Accessor<T>;
  },
): Accessor<T[]>;

#<Range>

Creates a list of elements by mapping a number range of specified start, to, and step.

All stop, to and step props are reactive, and changing them will cause the elements array to be recalculated, creating new elements for numbers added to the range.

• start defaults to 0.

• to defaults to 1. Range stops at to, it is not included in the range.

• step will become negative (the range will be descending) if to is smaller than start.

<Range start={2} to={14} step={0.5}>
   <div></div>
</Range>

// with a render prop:
<Range start={2} to={14} step={0.5}>
   {n => <div>{n}</div>}
</Range>

// with fallback:
<Range to={0}  fallback={<p>no items...</p>}>
   <div></div>
</Range>

Array spread shortcut:

const [start, setStart] = createSignal(0);
const [to, setTo] = createSignal(10);
const [step, setStep] = createSignal(2);

<Range {...[start, to, step]} />
<Range {...[0, 10, 2]} />
<Range start={start()} to={to()} step={step()} />

#Definition

RangeProps is an interface of stop, to and step props, OR 0, 1 and 2 indexes of a spread array.

function Range<T>(
  props: RangeProps & {
    fallback?: T;
    children: ((number: number) => T) | T;
  },
): Accessor<T[]>;

#indexRange

Primitive for mapping a number range of specified stop, to and step, while keeping previous elements of the same index. Underlying helper for the <IndexRange> control flow.

All stop, to and step arguments are accessors, and changing them will cause the mapped array to be recalculated, mapping new items appended at the end of the range.

step will become negative (the range will be descending) if to is smaller than start. Range stops at to, it is not included in the range.

const [to, setTo] = createSignal(5);
const mapped = indexRange(
  () => 0,
  to,
  () => 0.5,
  number => {
    const [value, setValue] = createSignal(number());
    createEffect(() => handleNewNumber(number()));
    return value;
  },
);
mapped(); // => [0, 0.5, 1, 1.5, 2...]
setTo(3); // changes the output array, mapping only added indexes

#Definition

function indexRange<T>(
  start: Accessor<number>,
  to: Accessor<number>,
  step: Accessor<number>,
  mapFn: (n: Accessor<number>) => T,
  options?: {
    fallback?: Accessor<T>;
  },
): Accessor<T[]>;

#<IndexRange>

Control Flow Component for displaying a number range of elements, where elements receive a number value as signal, by mapping a number range of specified start, to, and step.

All stop, to and step props are reactive, and changing them will cause the elements array to be recalculated, creating new elements for numbers added to the range.

• start defaults to 0.

• to defaults to 1. Range stops at to, it is not included in the range.

• step will become negative (the range will be descending) if to is smaller than start.

<IndexRange start={2} to={14} step={0.5}>
   <div></div>
</IndexRange>

// with a render prop:
<IndexRange start={2} to={14} step={0.5}>
   {n => <div>{n()}</div>}
</IndexRange>

// with fallback:
<IndexRange to={0}  fallback={<p>no items...</p>}>
   <div></div>
</IndexRange>

Array spread shortcut:

const [start, setStart] = createSignal(0);
const [to, setTo] = createSignal(10);
const [step, setStep] = createSignal(2);

<IndexRange {...[start, to, step]} />
<IndexRange {...[0, 10, 2]} />
<IndexRange start={start()} to={to()} step={step()} />

#Definition

RangeProps is an interface of stop, to and step props, OR 0, 1 and 2 indexes of a spread array.

function IndexRange<T>(
  props: RangeProps & {
    fallback?: T;
    children: ((number: Accessor<number>) => T) | T;
  },
): Accessor<T[]>;

#Demo

Live Site

Codesandbox: CodeSandbox

#Possible improvements

#(PRs Welcome)

• Currently the mapRange is handling decremanting ranges by swapping start and to with each other, and then cloning and reversing the mapped array. Doing this during the range mapping could possibly be more performant.
• For Ranges, because of how numbers are calculated, fractions might sometimes loose precision. E.g. a range from 1.64 to 2 by 0.2 step would generate numbers: [1.64, 1.8399999999999999] instead of [1.64, 1.84].
• Both mapRange and indexRange are missing index arguments in the mapping function.

#Changelog

See CHANGELOG.md