react-native-big-list/lib/utils.js

High-performance, virtualized list for React Native. Efficiently renders large datasets with recycler API for smooth scrolling and low memory usage. Ideal for fast, scalable, customizable lists on Android, iOS, and web.

import React from "react";

/**
 * Is numeric.
 * @param {any} num
 * @returns {boolean}
 */
export const isNumeric = (num) => {
  return !isNaN(parseFloat(num)) && isFinite(num);
};

/**
 * Process block.
 * @param {number} containerHeight
 * @param {number} scrollTop
 * @param {number|null|undefined} batchSizeThreshold
 * @returns {{blockStart: number, batchSize: number, blockEnd: number}}
 */
export const processBlock = ({
  containerHeight,
  scrollTop,
  batchSizeThreshold = 1,
}) => {
  if (containerHeight === 0) {
    return {
      batchSize: 0,
      blockStart: 0,
      blockEnd: 0,
    };
  }
  const batchSize = Math.ceil(
    containerHeight * Math.max(0.5, batchSizeThreshold),
  );
  const blockNumber = Math.ceil(scrollTop / batchSize);
  const blockStart = batchSize * blockNumber;
  const blockEnd = blockStart + batchSize;
  return { batchSize, blockStart, blockEnd };
};

/**
 * Autobind context to class methods.
 * @param {object} self
 * @returns {{}}
 */
export const autobind = (self = {}) => {
  const exclude = [
    "componentWillMount",
    /UNSAFE_.*/,
    "render",
    "getSnapshotBeforeUpdate",
    "componentDidMount",
    "componentWillReceiveProps",
    "shouldComponentUpdate",
    "componentWillUpdate",
    "componentDidUpdate",
    "componentWillUnmount",
    "componentDidCatch",
    "setState",
    "forceUpdate",
  ];

  const filter = (key) => {
    const match = (pattern) =>
      typeof pattern === "string" ? key === pattern : pattern.test(key);
    if (exclude) {
      return !exclude.some(match);
    }
    return true;
  };

  const getAllProperties = (object) => {
    const properties = new Set();
    do {
      for (const key of Object.getOwnPropertyNames(object).concat(
        Object.getOwnPropertySymbols(object),
      )) {
        properties.add([object, key]);
      }
    } while (
      (object = Object.getPrototypeOf(object)) &&
      object !== Object.prototype
    );
    return properties;
  };

  for (const [object, key] of getAllProperties(self.constructor.prototype)) {
    if (key === "constructor" || !filter(key)) {
      continue;
    }
    const descriptor = Object.getOwnPropertyDescriptor(object, key);
    if (descriptor && typeof descriptor.value === "function") {
      self[key] = self[key].bind(self);
    }
  }
  return self;
};

/**
 * Merge styles
 * @param {array|object|null|undefined} style
 * @param {array|object} defaultStyle
 * @returns {Object}
 */
export const mergeViewStyle = (style, defaultStyle = {}) => {
  let mergedStyle = style;
  if (mergedStyle == null) {
    mergedStyle = defaultStyle;
  } else if (Array.isArray(style) && Array.isArray(defaultStyle)) {
    const mergedDefaultStyle = [...defaultStyle];
    mergedDefaultStyle.concat(style);
    mergedStyle = mergedDefaultStyle;
  } else if (Array.isArray(defaultStyle)) {
    const mergedDefaultStyle = [...defaultStyle];
    mergedDefaultStyle.push(style);
    mergedStyle = mergedDefaultStyle;
  } else if (Array.isArray(style)) {
    mergedStyle = [...style];
    mergedStyle.unshift(defaultStyle);
  } else {
    mergedStyle = [defaultStyle, style];
  }
  return mergedStyle;
};

/**
 * Get element from component.
 * @param {React.node} Component
 * @param props
 * @returns {JSX.Element|[]|*}
 */
export const createElement = (Component, props = {}) => {
  return Component != null ? (
    React.isValidElement(Component) ? (
      React.cloneElement(Component, props)
    ) : (
      <Component {...props} />
    )
  ) : null;
};