JQuery $.each traverses JavaScript array object instances_jquery

View a simple jQuery example to iterate over a JavaScript array object.

var json = [
{"id":"1","tagName":"apple"},
{"id":"2","tagName":"orange"},
{"id":"3","tagName":"banana"},
{"id":"4","tagName":"watermelon"},
{"id":"5","tagName":"pineapple"}
];

$.each(json, function(idx, obj) {
alert(obj.tagName);
});

The above code snippet works fine, prompting “apple”, “orange”…etc., as expected.
Problem: JSON string

The following example declares a JSON string (enclosed in single or double quotes) directly.

var json = '[{"id":"1","tagName":"apple"},{"id":"2","tagName":"orange"},
{"id":"3","tagName":"banana"},{"id":"4","tagName":"watermelon"},
{"id":"5","tagName":"pineapple"}]';

$.each(json, function(idx, obj) {
alert(obj.tagName);
});

In Chrome it shows the following error in the console:

Uncaught TypeError: Cannot use 'in' operator to search for '156'
in [{"id":"1","tagName":"apple"}...

Solution: Convert JSON string to JavaScript object.
To fix it, convert it to a JavaScript object via standard JSON.parse() or jQuery's $.parseJSON .

var json = '[{"id":"1","tagName":"apple"},{"id":"2","tagName":"orange"},
{"id":"3","tagName":"banana"},{"id":"4","tagName":"watermelon"},
{"id":"5","tagName":"pineapple"}]';

$.each(JSON.parse(json), function(idx, obj) {
alert(obj.tagName);
});

//or 

$.each($.parseJSON(json), function(idx, obj) {
alert(obj.tagName);
});