littleReact/src/Children.js

import { getIteractor } from './may-dom/Iteractor';
export const Children = {
    only: function (child) {
        if (child && !Array.isArray(child)) {
            return child;
        }
        if (child && child.length === 1 && child[0].mtype) {
            return child[0];
        }
        throw new Error("expect only one child");
    },
    forEach: function (children, callback, context) {
        var ret;
        if (!children) {
            return null;
        }
        ret = toArray(children);

        ret.forEach(callback, context);
        return ret;

    },
    map: function (children, callback, context) {
        var ret = [];
        if (children == null) {
            //null 或undefinded直接返回
            return children;
        }
        toArray(children).forEach(function (item, index) {
            var res = callback.call(context, item, index);
            if (res == null) {
                return;
            } else {
                ret.push(res);
            }
        });
        return ret;

    },
    toArray: function (children) {
        if (children == null) {
            return [];
        }
        return toArray(children);
    }
}
function toArray(children) {
    var ret = [];
    if (Array.isArray(children)) {
        for (var i = 0; i < children.length; i++) {
            var c = children[i];
            if (c.type) {
                ret.push(c);
            } else { //有可能是子数组iterator
                var iteratorFn = getIteractor(c);
                if (iteratorFn) {
                    var iterators = callIteractor(iteratorFn, c);
                    for (var _i = 0; _i < iterators.length; _i++) {
                        ret.push(iterators[_i]);
                    }
                } else {
                    ret.push(c);
                }
            }
        }
    } else {
        ret.push(children);
    }
    return ret;
}