普通js通常這樣轉換

//這是一個json物件
var jsonobj = {"sztno":"330890811","transTime":"2018-5-7 08:00:36","amt":"50"};
//json物件轉成json字串
var jsonstr = JSON.stringify(jsonobj)
console.log("jsonstr=="+jsonstr)
//列印結果:"jsonstr=={"sztno":"330890811","transTime":"2018-5-7 08:00:36","amt":"50"}"

//由json字串轉成json物件
var obj1 = eval('(' + jsonstr + ')'
 
);
var obj2 = JSON.parse(jsonstr); 
console.log("json obj1=="+JSON.stringify(obj1))
//列印結果:"obj1=={"sztno":"330890811","transTime":"2018-5-7 08:00:36","amt":"50"}"
console.log("json obj2=="+JSON.stringify(obj2))
//列印結果:"obj2=={"sztno":"330890811","transTime":"2018-5-7 08:00:36","amt":"50"}"

微信小程式

//這是一個json物件
var jsonobj = {"sztno"
 
:"330890811","transTime":"2018-5-7 08:00:36","amt":"50"};
//json物件轉成json字串（同普通js中相同）
var jsonstr = JSON.stringify(jsonobj)
console.log("jsonstr=="+jsonstr)
//列印結果:"jsonstr=={"sztno":"330890811","transTime":"2018-5-7 08:00:36","amt":"50"}"

//由json字串轉成json物件，eval()函式在小程式用不了，被小程式禁用了
var obj1 = JSON.parse(jsonstr); //可用此方法來轉換
 

console.log("json obj1=="+JSON.stringify(obj1))
//列印結果:"obj1=={"sztno":"330890811","transTime":"2018-5-7 08:00:36","amt":"50"}"