查看一個簡單的jQuery的例子來遍歷一個JavaScript數組對象。
var json = [{"id":"1","tagName":"apple"},{"id":"2","tagName":"orange"},{"id":"3","tagName":"banana"},{"id":"4","tagName":"watermelon"},{"id":"5","tagName":"pineapple"}];$.each(json, function(idx, obj) {alert(obj.tagName);}); 上面的代碼片斷工作正常，提示 “apple”, “orange” … 等，如預期一樣。
問題: JSON 字符串
下面的例子中，聲明了一個JSON字符串（隨附單或雙引號）直接地。
var json = '[{"id":"1","tagName":"apple"},{"id":"2","tagName":"orange"},{"id":"3","tagName":"banana"},{"id":"4","tagName":"watermelon"},{"id":"5","tagName":"pineapple"}]';$.each(json, function(idx, obj) {alert(obj.tagName);}); 在Chrome中，它顯示在控制臺下面的錯誤：
Uncaught TypeError: Cannot use 'in' operator to search for '156'
in [{"id":"1","tagName":"apple"}...
解決方案：JSON字符串轉換為JavaScript對象。
要修復它，通過標準JSON.parse()或jQuery 的 $.parseJSON 將其轉換為JavaScript對象。
var json = '[{"id":"1","tagName":"apple"},{"id":"2","tagName":"orange"},{"id":"3","tagName":"banana"},{"id":"4","tagName":"watermelon"},{"id":"5","tagName":"pineapple"}]';$.each(JSON.parse(json), function(idx, obj) {alert(obj.tagName);});//or $.each($.parseJSON(json), function(idx, obj) {alert(obj.tagName);}); 
