37 lines
1.1 KiB
Markdown
37 lines
1.1 KiB
Markdown
**Error**!
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Try it:
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```js run
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let user = {
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name: "John",
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go: function() { alert(this.name) }
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}
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(user.go)() // error!
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```
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The error message in most browsers does not give understanding what went wrong.
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**The error appears because a semicolon is missing after `user = {...}`.**
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JavaScript does not auto-insert a semicolon before a bracket `(user.go)()`, so it reads the code like:
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```js no-beautify
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let user = { go:... }(user.go)()
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```
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Then we can also see that such a joint expression is syntactically a call of the object `{ go: ... }` as a function with the argument `(user.go)`. And that also happens on the same line with `let user`, so the `user` object has not yet even been defined, hence the error.
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If we insert the semicolon, all is fine:
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```js run
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let user = {
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name: "John",
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go: function() { alert(this.name) }
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}*!*;*/!*
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(user.go)() // John
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```
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Please note that brackets around `(user.go)` do nothing here. Usually they setup the order of operations, but here the dot `.` works first anyway, so there's no effect. Only the semicolon thing matters.
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