jQuery loop over JSON字元串 – $.each實例

先來一段簡單的javascript對象的遍歷：

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);
});

當為JSON字元串時：

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,他會顯示 錯誤:

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

解決方案：

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);
});