javascript what does range.endOffset() give you?

问题

When I go:

range.selectNodeContents(element);

My understanding is that the range object selects all the contents of element. So that would mean that if I said:

range.startOffset();

I should get 0. Which is true when testing. But then if I say:

range.endOffset();

I would think that I get the length of the contents of the element. But I don't. I get 1, or 3... or numbers I don't understand.

So... what does range.endOffset() really tell you?

回答1:

The Range.endOffset read-only property returns a number representing where in the Range.endContainer the Range ends.

From: https://developer.mozilla.org/en-US/docs/Web/API/Range/endOffset

回答2:

When you use selectNodeContents,

2. Let length be the length of node.

4. Set end to the boundary point (node, length).

So the end offset is set to the length of the node:

To determine the length of a node node, switch on node:

• DocumentType
  Zero.

• Text, ProcessingInstruction, Comment
  The number of code units in its data.

• Any other node
  Its number of children.

That's what you will get you you call endOffset.

来源：https://stackoverflow.com/questions/39812835/javascript-what-does-range-endoffset-give-you