ดูสิ่งมีกุญแจจาวาสคริปต์
รหัสตัวอย่าง
วิธีตรวจสอบว่าสิ่งมีกุญแจจาวาสคริปต์
myObj.hasOwnProperty('key') // it checks object for particular key and not on prototype จาวาสคริปต์โปรดตรวจสอบว่ากุญแจอยู่ในวัตถุ
"key" in obj // true, regardless of the actual value
If you want to check if a key doesn't exist, remember to use parenthesis:
!("key" in obj) // true if "key" doesn't exist in object
!"key" in obj // ERROR! Equivalent to "false in obj"
Or, if you want to particularly test for properties of the object instance (and not inherited properties), use hasOwnProperty:
obj.hasOwnProperty("key") // trueหน้าคล้ายกัน
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