# All files useThrottledFunction.ts

100% Statements 130/130
100% Branches 10/10
100% Functions 1/1
100% Lines 130/130

Press n or j to go to the next uncovered block, b, p or k for the previous block.

    1
    2
    3
    4
    5
    6
    7
    8
    9
    10
    11
    12
    13
    14
    15
    16
    17
    18
    19
    20
    21
    22
    23
    24
    25
    26
    27
    28
    29
    30
    31
    32
    33
    34
    35
    36
    37
    38
    39
    40
    41
    42
    43
    44
    45
    46
    47
    48
    49
    50
    51
    52
    53
    54
    55
    56
    57
    58
    59
    60
    61
    62
    63
    64
    65
    66
    67
    68
    69
    70
    71
    72
    73
    74
    75
    76
    77
    78
    79
    80
    81
    82
    83
    84
    85
    86
    87
    88
    89
    90
    91
    92
    93
    94
    95
    96
    97
    98
    99
    100
    101
    102
    103
    104
    105
    106
    107
    108
    109
    110
    111
    112
    113
    114
    115
    116
    117
    118
    119
    120
    121
    122
    123
    124
    125
    126
    127
    128
    129
    130
    1311x
    1x
    1x
    1x
    1x
    1x
    1x
    1x
    1x
    1x
    1x
    1x
    1x
    1x
    1x
    1x
    1x
    1x
    1x
    1x
    1x
    1x
    1x
    1x
    1x
    1x
    1x
    1x
    1x
    1x
    1x
    1x
    1x
    1x
    1x
    1x
    1x
    1x
    1x
    1x
    1x
    1x
    1x
    1x
    1x
    1x
    1x
    1x
    1x
    1x
    1x
    1x
    1x
    1x
    1x
    1x
    1x
    1x
    1x
    1x
    1x
    1x
    1x
    1x
    1x
    1x
    1x
    1x
    1x
    1x
    1x
    1x
    1x
    1x
    1x
    1x
    1x
    1x
    1x
    1x
    1x
    1x
    1x
    1x
    1x
    1x
    1x
    1x
    21x
    21x
    21x
    21x
    21x
    21x
    21x
    21x
    21x
    21x
    21x
    21x
    21x
    21x
    2x
    2x
    2x
    21x
    21x
    21x
    21x
    16x
    16x
    16x
    16x
    16x
    2x
    2x
    16x
    3x
    2x
    2x
    2x
    2x
    3x
    3x
    16x
    16x
    16x
    21x
    21x
    21x
     import { useCallback, useEffect, useRef } from "react";
    import type { AnyFunction } from "./types";
    import { useIsomorphicLayoutEffect } from "./useIsomorphicLayoutEffect";

    /**
     * @remarks \@since 6.0.0
     */
    export type ThrottledFunction<F extends AnyFunction> = (
      ...args: Parameters<F>
    ) => ReturnType<F>;

    /**
     * Creates a function that will only be called once every X milliseconds.
     *
     * @example
     * Throttling Search API Requests
     * ```tsx
     * import { TextField, useThrottledFunction, useUnmounted } from "@react-md/core";
     * import { useState } from "react";
     * import type { ReactElement } from "react";
     *
     * interface State {
     *   error?: unknown
     *   loading: boolean;
     *   results?: {
     *     // pretend some search results
     *     id: string;
     *     name: string;
     *   }[];
     * }
     *
     * function Example(): ReactElement {
     *   const [state, setState] = useState<State>({
     *     loading: false,
     *   });
     *   // this is only required for async actions
     *   const unmounted = useUnmounted();
     *
     *   // A new search request will be fired once every 500ms as the user types.
     *   // can't use the event here since React uses synthetic events
     *   const search = useThrottledFunction(async (q: string) => {
     *     setState({
     *       loading: true,
     *       error: undefined,
     *       results: undefined,
     *     });
     *
     *     try {
     *       const response = await fetch('/search', {
     *         method: 'POST',
     *         headers: {
     *           'Content-Type': 'application/json',
     *         },
     *         body: JSON.stringify({ q }),
     *       });
     *       const json = await response.json();
     *
     *       if (!unmounted.current) {
     *         setState({
     *           loading: false,
     *           results: json,
     *         });
     *       }
     *     } catch (error) {
     *       if (!unmounted.current) {
     *         setState({
     *           error,
     *           loading: false,
     *         });
     *       }
     *     }
     *   }, 500);
     *
     *   return (
     *     <TextField
     *       type="search"
     *       label="Search"
     *       onChange={(event) => search(event.currentTarget.value)}
     *     />
     *   );
     * }
     * ```
     *
     * @see `useDebouncedFunction` for debounce behavior instead. (Call a
     * function only if it has not been called again for X milliseconds).
     * @remarks \@since 6.0.0
     */
    export function useThrottledFunction<F extends AnyFunction>(
      func: F,
      wait: number
    ): ThrottledFunction<F> {
      const args = useRef<Parameters<F>>();
      const result = useRef<ReturnType<F>>();
      const timeout = useRef<number | undefined>();
      const funcRef = useRef(func);
      const lastCalledTime = useRef(0);

      useIsomorphicLayoutEffect(() => {
        funcRef.current = func;
      });

      useEffect(() => {
        return () => {
          window.clearTimeout(timeout.current);
        };
      }, []);

      return useCallback(
        (...nextArgs) => {
          args.current = nextArgs;

          const now = Date.now();
          const remaining = wait - (now - lastCalledTime.current);
          if (remaining <= 0 || remaining > wait) {
            lastCalledTime.current = now;
            result.current = funcRef.current(...args.current);
          } else if (!timeout.current) {
            timeout.current = window.setTimeout(() => {
              lastCalledTime.current = Date.now();
              timeout.current = undefined;
              // should exist by this time
              result.current = funcRef.current(...(args.current as Parameters<F>));
            }, remaining);
          }

          return result.current as ReturnType<F>;
        },
        [wait]
      );
    }