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Quang Van
Quang Van

Reputation: 12095

AngularJS conditionals in HTML Attribute

How would you change an html attribute based on the model?

I'm trying to change an input's placeholder text based on a length of an array:

<input placeholder="{{todos.length ? 'Insert todo' : 'Insert your first todo'}}" />

But that doesn't seem to work...

JS Bin code example.

Upvotes: 19

Views: 23224

Answers (2)

Ben Brandt
Ben Brandt

Reputation: 2921

For anyone else who comes across this (like I just did via Google), it looks like Angular recently added support for the ternary operator in expressions. I just used it successfully in 1.2.16 to dynamically update a tooltip (title) attribute. It seems to have first appeared in the documentation for 1.2.17, although they still generally discourage its use:

From: AngularJS: Developer Guide: Expressions

Apart from the ternary operator (a ? b : c), you cannot write a control flow statement in an expression. The reason behind this is core to the Angular philosophy that application logic should be in controllers, not the views. If you need a real conditional, loop, or to throw from a view expression, delegate to a JavaScript method instead.

Upvotes: 10

jaime
jaime

Reputation: 42031

The ternary operator doesn't seem to work in this case, instead of doing this

{{cond ? true : false}}

Change it to

{{ exp && true || false }}

So your placeholder attribute would look like this (I have shortened it for demonstration purposes)

placeholder="{{todos.length > 0 && 'Insert' || 'Insert first'}}"

Upvotes: 26

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