JSON and XML

This page covers converting between text and data with the JSON and XML objects, and reading XML documents.

Topics on this page:

• JSON: JSON.parse, JSON.stringify, example
• XML: XML.parse, XML.stringify, XML node members, querying lists of nodes

See also: Lists and Maps, HTTP and Utilities.

JSON objects become maps and JSON arrays become lists, so you can use all map and list features on parsed data.

Parses a JSON string and returns the resulting map, list, string, number, boolean, or null.

If text is not valid JSON, or is not a string, the result is null. No script error is raised, so check the result before you use it.

data = JSON.parse('{"name": "Pump 1", "readings": [12.5, 13, 14.25], "ok": true}');
print(data.name, "\n");
print(data.readings[1], " ", data.readings.length, "\n");
print(JSON.parse("not json"), "\n");
return data.ok;

Print output:

Pump 1
13 3
null

Output: true

If you send a parsed map or list to an output property of a Script block, the value is converted to text when the property is a string property.

Converts a map, list, string, number, boolean, or null to a JSON string.

• indent — optional. A number of spaces, or a string, to indent each level. Without indent the result is on one line.

value can contain only JSON values. A DateTime, an XML node, a page model object, NaN or Infinity causes an error. Convert dates to strings first, for example with dateFormat.

obj = {a: 1, b: [1, 2], c: null};
print(JSON.stringify(obj), "\n");
print(JSON.stringify("say \"hi\""), "\n");
return JSON.stringify({a: 1, b: [1, 2]}, 2);

Print output:

{"a":1,"b":[1,2],"c":null}
"say \"hi\""

Output:

{
  "a": 1,
  "b": [
    1,
    2
  ]
}

The following example uses a for loop to print the id of each menu item and prints dashes for null items. print does not add line breaks, so the output is one line.

json = {"menu": {
    "header": "SVG Viewer",
    "items": [
        {"id": "Open"},
        {"id": "OpenNew", "label": "Open New"},
        null,
        {"id": "ZoomIn", "label": "Zoom In"},
        {"id": "ZoomOut", "label": "Zoom Out"},
        {"id": "OriginalView", "label": "Original View"},
        null,
        {"id": "Quality"},
        {"id": "Pause"},
        {"id": "Mute"},
        null,
        {"id": "Find", "label": "Find..."},
        {"id": "FindAgain", "label": "Find Again"},
        {"id": "Copy"},
        {"id": "CopyAgain", "label": "Copy Again"},
        {"id": "CopySVG", "label": "Copy SVG"},
        {"id": "ViewSVG", "label": "View SVG"},
        {"id": "ViewSource", "label": "View Source"},
        {"id": "SaveAs", "label": "Save As"},
        null,
        {"id": "Help"},
        {"id": "About", "label": "About SVG Viewer..."}
    ]
}};
 
print(json.menu.header);
 
for (var i = 0; i < json.menu.items.length; i++) {
    if (json.menu.items[i] == null) {
        print("----");
    } else {
        print(json.menu.items[i].id);
    }
}
return json.menu.items.length;

Print output:

SVG ViewerOpenOpenNew----ZoomInZoomOutOriginalView----QualityPauseMute----FindFindAgainCopyCopyAgainCopySVGViewSVGViewSourceSaveAs----HelpAbout

Output: 22

Parses an XML string and returns its root element. If text is not well-formed XML, a script error occurs. If text is not a string, the result is null.

xml = XML.parse('<p id="a">b</p>');
return xml.name;

Output: p

Converts an XML element back to an XML string. If the value is not an XML element, the result is null.

xml = XML.parse('<p id="a">b</p>');
return XML.stringify(xml);

Output: <p id="a">b</p>

query and queryAll search the descendants of the node, depth first, by element name. The node itself is not checked. When an element matches, its own descendants are not searched, so queryAll does not return a matching element that is nested inside another matching element. The name is a plain element name; paths and CSS-style selectors are not supported.

xml = XML.parse('<a><b>B 1<c>C 1</c></b><b att="2">B 2</b></a>');
print(xml.query("b").children.join(","), "\n");
print(xml.query("b").elements.join(","), "\n");
print(xml.query("b").text, "\n");
print(xml.query("c").text, "\n");
print(xml.query("b").children[0].data, "\n");
print(xml.queryAll("b").length, "\n");
print(xml.queryAll("b")[1].getAttribute("att"), "\n");
print(xml.query("missing"), "\n");
xml.query("c").remove();
return XML.stringify(xml);

Print output:

B 1,<c>C 1</c>
<c>C 1</c>
null
C 1
B 1
2
2
null

Output: <a><b>B 1</b><b att="2">B 2</b></a>

A list of XML nodes returned by children, elements or queryAll also has query(name) and queryAll(name). They search each node in the list in the same way. Unlike the element methods, a node in the list is itself checked against the name.

These methods return null when the list is empty or is not a list returned by an XML member (for example a list you built with [ ]).

xml = XML.parse('<root><group><item>1</item><item>2</item></group><group><item>3</item></group></root>');
groups = xml.queryAll("group");
items = groups.queryAll("item");
values = items.map(function (n) { return n.text; });
print(values.join(","), "\n");
return groups.query("item").text;

Print output:

1,2,3

Output: 1

src = '<rss><channel><title>News</title>' +
    '<item><title>First</title><link>http://a.example</link></item>' +
    '<item><title>Second</title><link>http://b.example</link></item>' +
    '</channel></rss>';
doc = XML.parse(src);
rows = [];
doc.queryAll("item").forEach(function (item) {
  rows.push({title: item.query("title").text, link: item.query("link").text});
});
print(doc.query("title").text, "\n");
return JSON.stringify(rows);

Print output:

News

Output: [{"title":"First","link":"http://a.example"},{"title":"Second","link":"http://b.example"}]