JSON Object Literals 物件文字 / 物件類型（解釋）
This is a JSON string:
'{"name":"John", "age":30, "car":null}'
Inside the JSON string there is a JSON object literal:
{"name":"John", "age":30, "car":null}
JSON object literals are surrounded by curly braces {}.
JSON object literals contains key/value pairs.
Keys and values are separated by a colon.
Each key/value pair is separated by a comma.
Keys must be strings, and values must be a valid JSON data type:
- string
- number
- object
- array
- boolean
- null
JavaScript Objects
You can create a JavaScript object from a JSON object literal:
myObj = {"name":"John", "age":30, "car":null};
Normally, you create a JavaScript object by parsing a JSON string:
myJSON = '{"name":"John", "age":30, "car":null}';
myObj = JSON.parse(myJSON);
Accessing Object Values 訪問物件值
You can access object values by using dot (.) notation:
const myJSON = '{"name":"John", "age":30, "car":null}';
const myObj = JSON.parse(myJSON);
x = myObj.name; //John
//也可以用[]
x = myObj["name"]; //John
Looping an Object 遍歷一個物件
You can loop through object properties with a for-in loop:
const myJSON = '{"name":"John", "age":30, "car":null}';
const myObj = JSON.parse(myJSON);
let text = "";
for (const x in myObj) {
text += x + ", ";
console.log(text); //name, age, car,
}
In a for-in loop, use the bracket notation to access the property values:
const myJSON = '{"name":"John", "age":30, "car":null}';
const myObj = JSON.parse(myJSON);
let text = "";
for (const x in myObj) {
text += myObj[x] + ", ";
}
console.log(text); //John, 30, null,
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