@blueprintjs/core/src/common/utils.ts

Core styles & components

/*
 * Copyright 2015 Palantir Technologies, Inc. All rights reserved.
 * Licensed under the BSD-3 License as modified (the “License”); you may obtain a copy
 * of the license at https://github.com/palantir/blueprint/blob/master/LICENSE
 * and https://github.com/palantir/blueprint/blob/master/PATENTS
 */

import { CLAMP_MIN_MAX } from "./errors";

// only accessible within this file, so use `Utils.isNodeEnv` from the outside.
declare var process: { env: any };

/** Returns whether `process.env.NODE_ENV` exists and equals `env`. */
export function isNodeEnv(env: string) {
    return typeof process !== "undefined" && process.env && process.env.NODE_ENV === env;
}

/** Returns whether the value is a function. Acts as a type guard. */
// tslint:disable-next-line:ban-types
export function isFunction(value: any): value is Function {
    return typeof value === "function";
}

/** Safely invoke the function with the given arguments, if it is indeed a function, and return its value. */
export function safeInvoke<R>(func: (() => R) | undefined): R;
export function safeInvoke<A, R>(func: ((arg1: A) => R) | undefined, arg1: A): R;
export function safeInvoke<A, B, R>(func: ((arg1: A, arg2: B) => R) | undefined, arg1: A, arg2: B): R;
export function safeInvoke<A, B, C, R>(
    func: ((arg1: A, arg2: B, arg3: C) => R) | undefined,
    arg1: A,
    arg2: B,
    arg3: C,
): R;
export function safeInvoke<A, B, C, D, R>(
    func: ((arg1: A, arg2: B, arg3: C, arg4: D) => R) | undefined,
    arg1: A,
    arg2: B,
    arg3: C,
    arg4: D,
): R;
// tslint:disable-next-line:ban-types
export function safeInvoke(func: Function | undefined, ...args: any[]) {
    if (isFunction(func)) {
        return func(...args);
    }
}

export function elementIsOrContains(element: HTMLElement, testElement: HTMLElement) {
    return element === testElement || element.contains(testElement);
}

/**
 * Returns the difference in length between two arrays. A `null` argument is considered an empty list.
 * The return value will be positive if `a` is longer than `b`, negative if the opposite is true,
 * and zero if their lengths are equal.
 */
export function arrayLengthCompare(a: any[] = [], b: any[] = []) {
    return a.length - b.length;
}

/**
 * Returns true if the two numbers are within the given tolerance of each other.
 * This is useful to correct for floating point precision issues, less useful for integers.
 */
export function approxEqual(a: number, b: number, tolerance = 0.00001) {
    return Math.abs(a - b) <= tolerance;
}

/** Clamps the given number between min and max values. Returns value if within range, or closest bound. */
export function clamp(val: number, min: number, max: number) {
    if (val == null) {
        return val;
    }
    if (max < min) {
        throw new Error(CLAMP_MIN_MAX);
    }
    return Math.min(Math.max(val, min), max);
}

/** Returns the number of decimal places in the given number. */
export function countDecimalPlaces(num: number) {
    if (typeof num !== "number" || Math.floor(num) === num) {
        return 0;
    }
    return num.toString().split(".")[1].length;
}

/**
 * Throttle an event on an EventTarget by wrapping it in a `requestAnimationFrame` call.
 * Returns the event handler that was bound to given eventName so you can clean up after yourself.
 * @see https://developer.mozilla.org/en-US/docs/Web/Events/scroll
 */
export function throttleEvent(target: EventTarget, eventName: string, newEventName: string) {
    const throttledFunc = throttleHelper(
        undefined,
        undefined,
        (event: Event) => {
            target.dispatchEvent(new CustomEvent(newEventName, event));
        },
    );
    target.addEventListener(eventName, throttledFunc);
    return throttledFunc;
};

export interface IThrottledReactEventOptions {
    preventDefault?: boolean;
};

/**
 * Throttle a callback by wrapping it in a `requestAnimationFrame` call. Returns the throttled
 * function.
 * @see https://www.html5rocks.com/en/tutorials/speed/animations/
 */
export function throttleReactEventCallback(
    callback: (event: React.SyntheticEvent<any>, ...otherArgs: any[]) => any,
    options: IThrottledReactEventOptions = {},
) {
    const throttledFunc = throttleHelper(
        (event2: React.SyntheticEvent<any>) => {
            if (options.preventDefault) {
                event2.preventDefault();
            }
        },
        (event2: React.SyntheticEvent<any>) => {
            // prevent React from reclaiming the event object before we reference it
            event2.persist();
        },
        (event2: React.SyntheticEvent<any>, ...otherArgs2: any[]) => {
            callback(event2, ...otherArgs2);
        },
    );
    return throttledFunc;
}

type ThrottleHelperCallback = (...args: any[]) => void;

function throttleHelper(
    onBeforeIsRunningCheck: ThrottleHelperCallback,
    onAfterIsRunningCheck: ThrottleHelperCallback,
    onAnimationFrameRequested: ThrottleHelperCallback,
) {
    let isRunning = false;
    const func = (...args: any[]) => {
        // don't use safeInvoke, because we might have more than its max number of typed params
        if (isFunction(onBeforeIsRunningCheck)) {
             onBeforeIsRunningCheck(...args);
        }

        if (isRunning) {
            return;
        }
        isRunning = true;

        if (isFunction(onAfterIsRunningCheck)) {
            onAfterIsRunningCheck(...args);
        }

        requestAnimationFrame(() => {
            if (isFunction(onAnimationFrameRequested)) {
                onAnimationFrameRequested(...args);
            }
            isRunning = false;
        });
    };
    return func;
}