heuristic manner

最新推荐文章于 2024-01-07 12:02:12 发布

原创最新推荐文章于 2024-01-07 12:02:12 发布 · 649 阅读

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本文探讨了jQuery中一种类型的检查方法，通过构造映射表来识别不同的对象类型，如DOM元素、数组、函数等，并深入讨论了浏览器环境中某些特性的实现细节。

due to there is no strict type checking, all the algorithms related to type checking are almost all heuristic progress,

“if there is a property of what, that could be xxx, or level down to other options”， you have to explore what it is through the way.

as this, in jquery.aop:

toStrings = {},
nodeTypes = { 1: 'element', 3: 'textnode', 9: 'document', 11: 'fragment' },
types = 'Arguments Array Boolean Date Document Element Error Fragment Function NodeList Null Number Object RegExp String TextNode Undefined Window'.split(' ');

//making a map of type
.....
return function(item) {
       return item == null && (item === undefined ? _undef : 'null') ||
	      item.nodeType && nodeTypes[item.nodeType] ||
	      typeof item.length == 'number' && (
	      item.callee && _arguments ||
	      item.alert && 'window' ||
	      item.item && 'nodelist') ||
	      toStrings[toString.call(item)];
};

- null or undefined;

- nodetype exist in object, it could be of types in nodeTypes, including the built-in ones, the BOM, DOM ones

-or when length property exist, it could be Arguments, NodeList, window

interestingly, in BOM, DOM field, the __proto__ chain searching property mechanism is NOT always work, e.g. length in window, but check it , u will find:

Object.prototype.hasOwnProperty.call(window, "length") //false in FF, true in chrome

Object.prototype.toString.call(window.__proto__, "length") //false
....
"length" in window //true,

//at least it can show that the implementation is not integrity somehow

-use Object.prototype.toString method to output its type information and use map constructed to output its type.