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dojo ยป query

Functiondojo.query (returns dojo.NodeList)

dojo.require("dojo._base.query");

dojo.query() is the swiss army knife of DOM node manipulation in Dojo. Much like Prototype’s “$$” (bling-bling) function or JQuery’s “$” function, dojo.query provides robust, high-performance CSS-based node selector support with the option of scoping searches to a particular sub-tree of a document.

Supported Selectors:

dojo.query() supports a rich set of CSS3 selectors, including:

  • class selectors (e.g., .foo)
  • node type selectors like span
  • descendant selectors
  • > child element selectors
  • #foo style ID selectors
  • * universal selector
  • ~, the immediately preceeded-by sibling selector
  • +, the preceeded-by sibling selector
  • attribute queries:
    • [foo] attribute presence selector
    • [foo='bar'] attribute value exact match
    • [foo~='bar'] attribute value list item match
    • [foo^='bar'] attribute start match
    • [foo$='bar'] attribute end match
    • [foo*='bar'] attribute substring match
  • :first-child, :last-child, and :only-child positional selectors
  • :empty content emtpy selector
  • :checked pseudo selector
  • :nth-child(n), :nth-child(2n+1) style positional calculations
  • :nth-child(even), :nth-child(odd) positional selectors
  • :not(...) negation pseudo selectors

Any legal combination of these selectors will work with dojo.query(), including compound selectors (“,” delimited). Very complex and useful searches can be constructed with this palette of selectors and when combined with functions for manipulation presented by dojo.NodeList, many types of DOM manipulation operations become very straightforward.

Unsupported Selectors:

While dojo.query handles many CSS3 selectors, some fall outside of what’s resaonable for a programmatic node querying engine to handle. Currently unsupported selectors include:

  • namespace-differentiated selectors of any form
  • all :: pseduo-element selectors
  • certain pseduo-selectors which don’t get a lot of day-to-day use:
    • :root, :lang(), :target, :focus
  • all visual and state selectors:
    • :root, :active, :hover, :visisted, :link, :enabled, :disabled
  • :*-of-type pseudo selectors

dojo.query and XML Documents:

dojo.query (as of dojo 1.2) supports searching XML documents in a case-sensitive manner. If an HTML document is served with a doctype that forces case-sensitivity (e.g., XHTML 1.1 Strict), dojo.query() will detect this and “do the right thing”. Case sensitivity is dependent upon the document being searched and not the query used. It is therefore possible to use case-sensitive queries on strict sub-documents (iframes, etc.) or XML documents while still assuming case-insensitivity for a host/root document.

Non-selector Queries:

If something other than a String is passed for the query, dojo.query will return a new dojo.NodeList instance constructed from that parameter alone and all further processing will stop. This means that if you have a reference to a node or NodeList, you can quickly construct a new NodeList from the original by calling dojo.query(node) or dojo.query(list).

parametertypedescription
queryStringThe CSS3 expression to match against. For details on the syntax of CSS3 selectors, see <http://www.w3.org/TR/css3-selectors/#selectors>
rootString|DOMNodeOptional. A DOMNode (or node id) to scope the search from. Optional.
listCtorFunctionOptional.

Usage

var foo: dojo.NodeList=dojo.query(query: String, root: String|DOMNode?, listCtor: Function?);

Examples

Example 1

search the entire document for elements with the class “foo”:

dojo.query(".foo");

these elements will match:

<span class="foo"></span>
<span class="foo bar"></span>
<p class="thud foo"></p>

Example 2

search the entire document for elements with the classes “foo” and “bar”:

dojo.query(".foo.bar");

these elements will match:

<span class="foo bar"></span>

while these will not:

<span class="foo"></span>
<p class="thud foo"></p>

Example 3

find elements which are descendants of paragraphs and which have a “highlighted” class:

dojo.query("p span.highlighted");

the innermost span in this fragment matches:

<p class="foo">
    <span>...
        <span class="highlighted foo bar">...</span>
    </span>
</p>

Example 4

set an “odd” class on all odd table rows inside of the table #tabular_data, using the > (direct child) selector to avoid affecting any nested tables:

dojo.query("#tabular_data > tbody > tr:nth-child(odd)").addClass("odd");

Example 5

remove all elements with the class “error” from the document and store them in a list:

var errors = dojo.query(".error").orphan();

Example 6

add an onclick handler to every submit button in the document which causes the form to be sent via Ajax instead:

dojo.query("input[type='submit']").onclick(function(e){
    dojo.stopEvent(e); // prevent sending the form
    var btn = e.target;
    dojo.xhrPost({
        form: btn.form,
        load: function(data){
            // replace the form with the response
            var div = dojo.doc.createElement("div");
            dojo.place(div, btn.form, "after");
            div.innerHTML = data;
            dojo.style(btn.form, "display", "none");
        }
    });
});