rc-hooks/lib/usePrevious/index.js

React Hooks Library.

"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
var tslib_1 = require("tslib");
var react_1 = require("react");
var useMountedRef_1 = tslib_1.__importDefault(require("../useMountedRef"));
/**
 * 返回上一次的 state 或 props 。
 *
 * @param state 需要记录变化的值。
 * @returns 上一次记录的值。
 * @example
 * const [value, setValue] = useState('');
 * // 上一次 state 的值。
 * const prevValue = usePrevious(value);
 */
function usePrevious(state) {
    var mountedRef = (0, useMountedRef_1.default)();
    var prevRef = (0, react_1.useRef)();
    var curRef = (0, react_1.useRef)(state);
    if (mountedRef.current && curRef.current !== state) {
        prevRef.current = curRef.current;
        curRef.current = state;
    }
    return prevRef.current;
}
exports.default = usePrevious;