xml - What is the difference between .// and //* in XPath?

Question

While finding the relative XPath via Firebug : it creates like

1. .//*[@id='Passwd']--------- what if we dont use dot at the start what it signifies?

2. Just add //* in the Xpath -- it highlights --- various page elements ---------- what does it signify?

Below are XPaths for Gmail password fields. What is significance of * ?

• .//*[@id='Passwd']

• //child::input[@type='password']

Answer 1

There are several distinct, key XPath concepts in play here...

Absolute vs relative XPaths (/ vs .)

• / introduces an absolute location path, starting at the root of the document.
• . introduces a relative location path, starting at the context node.

Named element vs any element (ename vs *)

• /ename selects an ename root element
  • ./ename selects all ename child elements of the current node.
• /* selects the root element, regardless of name.
  • ./* or * selects all child elements of the context node, regardless of name.

descendant-or-self axis (//*)

• //ename selects all ename elements in a document.
  • .//ename selects all ename elements at or beneath the context node.
• //* selects all elements in a document, regardless of name.
  • .//* selects all elements, regardless of name, at or beneath the context node.

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With these concepts in mind, here are answers to your specific questions...

• .//*[@id='Passwd'] means to select all elements at or beneath the current context node that have an id attribute value equal to 'Passwd'.
• //child::input[@type='password'] can be simplified to //input[@type='password'] and means to select all input elements in the document that have an type attribute value equal to 'password'.