JSON Array Literals 陣列文字（解釋）
This is a JSON string:
'["Ford", "BMW", "Fiat"]' //string
Inside the JSON string there is a JSON array literal:
["Ford", "BMW", "Fiat"] // object
Arrays in JSON are almost the same as arrays in JavaScript.
In JSON, array values must be of type string, number, object, array, boolean or null.
In JavaScript, array values can be all of the above, plus any other valid JavaScript expression, including functions, dates, and undefined.
JavaScript Arrays
You can create a JavaScript array from a literal:
myArray = ["Ford", "BMW", "Fiat"];
You can create a JavaScript array by parsing a JSON string:
myJSON = '["Ford", "BMW", "Fiat"]';
myArray = JSON.parse(myJSON);
Accessing Array Values 訪問陣列值
You access array values by index:
const myJSON = '["Ford", "BMW", "Fiat"]';
const myArray = JSON.parse(myJSON);
myArray[0]; //Ford
Arrays in Objects
Objects can contain arrays:
{
"name":"John",
"age":30,
"cars":["Ford", "BMW", "Fiat"]
}
You access array values by index:
myObj.cars[0]; //Ford
Looping Through an Array 遍歷一個陣列
You can access array values by using a for in loop:
for (let i in myObj.cars) {
x += myObj.cars[i];
}
Or you can use a for loop:
for (let i = 0; i < myObj.cars.length; i++) {
x += myObj.cars[i];
}
完整程式碼
const myJSON = '{"name":"John", "age":30, "cars":["Ford", "BMW", "Fiat"]}';
const myObj = JSON.parse(myJSON);
let text = "";
for (let i in myObj.cars) {
text += myObj.cars[i] + ", ";
}
console.log(text);
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