javascript - 为什么简单地使用 ng-init 和 delete 会产生语法错误？

Question

这个简单的片段(jsfiddle):

<div ng-app="App" ng-init="foo={a: 20}; delete foo['a']">
</div>

创建此syntax error在 FF 和 Chrome 中。为什么？

Syntax Error: Token 'foo' is an unexpected token at column 21 of the expression [foo={a: 20}; delete foo['a']] starting at [foo['a']].

无论我尝试delete foo['a']还是delete foo.a都没有关系 - 两者都可以在vanilla javascript中工作；在 ng-init 中都不起作用。

Answer 1

嗯，显然ngInit想要一个expression ，它是 AngularJS 解析器可以理解的 JS 子集。

Expressions are JavaScript-like code snippets that are usually placed in bindings such as {{ expression }}. Expressions are processed by the $parse service. Expressions are often post processed using filters to create a more user-friendly format.

It might be tempting to think of Angular view expressions as JavaScript expressions, but that is not entirely correct, since Angular does not use a JavaScript eval() to evaluate expressions.

(强调我的)

因此$parse不支持delete。

另外，ngInit 文档说:

The only appropriate use of ngInit is for aliasing special properties of ngRepeat, as seen in the demo below. Besides this case, you should use controllers rather than ngInit to initialize values on a scope.