JavaScript 语言精粹代码片段

// 模拟 new 的行为
Function.prototype.method = function (name, func) {
  this.prototype[name] = func;
  return this;
};

Function.method("new", function () {
  var that = Object.create(this.prototype);
  var obj = this.apply(that, arguments);
  return (typeof obj === "object" && obj) || that;
});

var Mammal = function (name) {
  this.name = name;
};

var human = Mammal.new("people");

// 模拟类
Object.create = function (o) {
  let F = function () {};
  F.prototype = o;
  return new F();
};

var mammal = function (spec) {
  var that = {};

  that.get_name = function () {
    return spec.name;
  };
  that.says = function () {
    return spec.saying || "";
  };
  return that;
};

var cat = function (spec) {
  spec.saying = spec.saying || "meow";
  var that = mammal(spec);
  that.purr = function (n) {
    var i,
      s = "";
    for (i = 0; i < n; i++) {
      if (s) {
        s += "-";
      }
      s += "r";
    }
    return s;
  };
  that.get_name = function () {
    return that.says() + " " + spec.name + " " + that.says();
  };
  return that;
};

Object.method("superior", function (name) {
  var that = this,
    method = that[name];
  return function () {
    debugger;
    console.log(method());
    method.apply(that, arguments);
  };
});

var coolcat = function (spec) {
  var that = cat(spec),
    super_get_name = that.superior("get_name");
  that.get_name = function (n) {
    return "like" + super_get_name() + "baby";
  };
  return that;
};

var mycat = coolcat({ name: "Bix" });

// 事件发射与监听
var eventuality = function (that) {
  var registry = {};
  that.fire = function (event) {
    var array,
      func,
      handler,
      i,
      type = typeof event === "string" ? event : event.type;
    if (registry.hasOwnProperty(type)) {
      array = registry[type];
      for (i = 0; i < array.length; i += 1) {
        handler = array[i];
        func = handler.method;
        if (typeof func === "string") {
          func = this[func];
        }
        func.apply(this, handler.parameters || [event]);
      }
    }
    return this;
  };
  that.on = function (type, method, parameters) {
    var handler = {
      method: method,
      parameters: parameters,
    };
    if (registry.hasOwnProperty(type)) {
      registry[type].push(handler);
    } else {
      registry[type] = [handler];
    }
    return this;
  };
  return that;
};

// 初始值为 initial 的 m（row） x n（column） 矩阵
Array.matrix = function (m, n, initial) {
  var a,
    i,
    j,
    mat = [];
  for (i = 0; i < m; i++) {
    a = [];
    for (j = 0; j < n; j++) {
      a[j] = initial;
    }
    mat[i] = a;
  }
  return mat;
};

// 遍历 DOM 树
const walk_dom = function walk(node, func) {
  func(node);
  node = node.firstChild;
  while (node) {
    walk(node, func);
    node = node.nextSibling;
  }
};

var body = document.body;

walk_dom(body, (node) => {
  this.count ? this.count++ : (this.count = 1);
});

console.log("I have so many dom: " + count);

// 根据属性排序数组
// Array.prototype.sort(comparefn), this is a comparefn creator
var by = function (name, minor) {
  return function (o, p) {
    if (typeof o === "object" && typeof p === "object" && o && p) {
      let a = o[name];
      let b = p[name];
      if (a === b) {
        return typeof minor === "function" ? minor(o, p) : 0;
      }
      if (typeof a === typeof b) {
        return a < b ? -1 : 1;
      }
      return typeof a < typeof b ? -1 : 1;
    } else {
      throw {
        name: "Error",
        message: "Expect an object when sorting by " + name,
      };
    }
  };
};

// 用 apply 实现 bind 方法
Function.prototype.bind = function (that) {
  var it = this;
  var slice = Array.prototype.slice;
  var args = slice.apply(arguments, [1]);

  return function () {
    it.apply(that, args.concat(slice.apply(arguments, [0])));
  };
};

// 把某些符号变成不于 html 冲突的 entity
String.method(
  "entityify",
  (function () {
    var character = {
      "<": "&lt;",
      ">": "&gt;",
      "&": "&amp;",
      '"': "&quot;",
    };
    return function () {
      return this.replace(/[<>&"]/g, function (c) {
        return character(c);
      });
    };
  })(),
);