objectIndex: function(obj) { var expression = this.text; var indexFn = this.expression(); this.consume(']'); return extend(function $parseObjectIndex(self, locals) { var o = obj(self, locals), //parseObjectLiteral，实际就是obj i = indexFn(self, locals), //$parseConstant，这里就是name v; ensureSafeMemberName(i, expression); if (!o) return undefined; v = ensureSafeObject(o[i], expression); return v; }, { assign: function(self, value, locals) { var key = ensureSafeMemberName(indexFn(self, locals), expression); // prevent overwriting of Function.constructor which would break ensureSafeObject check var o = ensureSafeObject(obj(self, locals), expression); if (!o) obj.assign(self, o = {}, locals); return o[key] = value; } }); }
很简单吧，obj[xx]和obj.x类似。大家自行阅读，我们再看一个函数调用的demo
var _l = new Lexer({}); var _p = new Parser(_l, '', {}); var demo = { "test": function(){ alert("welcome"); } }; var a = _p.parse('test()'); console.log(a(demo));
我们传入一个test的调用。这边调用了parser中的functionCall方法和identifier方法
identifier: function() { var id = this.consume().text; //Continue reading each `.identifier` unless it is a method invocation while (this.peek('.') && this.peekAhead(1).identifier && !this.peekAhead(2, '(')) { id += this.consume().text + this.consume().text; } return getterFn(id, this.options, this.text); }
看一下getterFn方法
... forEach(pathKeys, function(key, index) { ensureSafeMemberName(key, fullExp); var lookupJs = (index // we simply dereference 's' on any .dot notation ? 's' // but if we are first then we check locals first, and if so read it first : '((l&&l.hasOwnProperty("' + key + '"))?l:s)') + '.' + key; if (expensiveChecks || isPossiblyDangerousMemberName(key)) { lookupJs = 'eso(' + lookupJs + ', fe)'; needsEnsureSafeObject = true; } code += 'if(s == null) return undefined;\n' + 's=' + lookupJs + ';\n'; }); code += 'return s;'; /* jshint -W054 */ var evaledFnGetter = new Function('s', 'l', 'eso', 'fe', code); // s=scope, l=locals, eso=ensureSafeObject /* jshint +W054 */ evaledFnGetter.toString = valueFn(code); ...
这是通过字符串创建一个匿名函数的方法。我们看下demo的test生成了一个什么匿名函数：
function('s', 'l', 'eso', 'fe'){ if(s == null) return undefined; s=((l&&l.hasOwnProperty("test"))?l:s).test; return s; }
这个匿名函数的意思，需要传入一个上下文，匿名函数通过查找上下文中是否有test属性，如果没有传上下文则直接返回未定义。这也就是为什么我们在生成好的a函数在执行它时需要传入demo对象的原因。最后补一个functionCall
functionCall: function(fnGetter, contextGetter) { var argsFn = []; if (this.peekToken().text !== ')') { /* 确认调用时有入参 */ do { //形参存入argsFn argsFn.push(this.expression()); } while (this.expect(',')); } this.consume(')'); var expressionText = this.text; // we can safely reuse the array across invocations var args = argsFn.length ? [] : null; return function $parseFunctionCall(scope, locals) { var context = contextGetter ? contextGetter(scope, locals) : isDefined(contextGetter) ? undefined : scope; //或者之前创建生成的匿名函数 var fn = fnGetter(scope, locals, context) || noop; if (args) { var i = argsFn.length; while (i--) { args[i] = ensureSafeObject(argsFn[i](scope, locals), expressionText); } } ensureSafeObject(context, expressionText); ensureSafeFunction(fn, expressionText); // IE doesn't have apply for some native functions //执行匿名函数的时候需要传入上下文 var v = fn.apply ? fn.apply(context, args) : fn(args[0], args[1], args[2], args[3], args[4]); if (args) { // Free-up the memory (arguments of the last function call). args.length = 0; } return ensureSafeObject(v, expressionText); }; }
下面我们看一下$ParseProvider，这是一个基于Lex和Parser函数的angular内置provider。它对scope的api提供了基础支持。