In js, variable objects have various problems of passing values and assigning values. Next I will introduce some issues about javascript variable objects to you. You can refer to them for reference.
I saw a piece of code on the Internet today, as shown below:
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Copytext Console. log (typeof (s); // function Var s = "1111 "; Function s (){} Console. log (typeof (s); // stringconsole. log (typeof (s); // function Var s = "1111 "; Function s (){} Console. log (typeof (s); // string |
After a long time, I finally figured out the variable object in JS.
The first line outputs the function, because after entering the scope, the variable object will first scan the function of the scope of course, and then scan the variable, then store the variable object, and then start to execute the code.
Therefore, the first line outputs the function.
The fourth line stores the variable object before the variable, so the second line of code s = "1111" overwrites the original function variable s, so the output string
Question about passing variable values into an object
The problem is as follows:
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Var o = 'left '; Var o1 = {drt: 'left '}; Var o2 = ['left'];
Var obj = {o: 333 }; Var obj1 = {o1 [drt]: 333 }; Var obj2 = {o2 [0]: 333 };
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The first three lines of the Code are several different declaration methods of variables, including common variables, objects, and arrays. The last three lines call these three variables and insert objects. Question:
1. Why is an error reported directly when obj1 and obj2 are declared?
2. No error is reported for obj, but why is the first attribute called "o" rather than the value of variable o "left" When looping its attributes?
If I want to pass a variable to an object as a property, and pass the variable value to the object as a property value, is it only used:
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Var o1 = {drt: 'left '}; Var obj3 = {drt: o1.drt} |
Variable assignment in class
The difference between object. prop and object [prop] assignment in Javascript.
To give a simple example, for example, you need to obtain the information of the open shard from stocks to form an openList object. The implementation code is as follows:
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Var stocks = { '000000': {'name': 'pudong Development Bank ', 'open': '9. 67', 'new': '9. 54 '}, '000000': {'name': 'baiyun Airport ', 'open': '6. 82', 'new': '6. 77 '}, '000000': {'name': 'steel & Steel stock ', 'open': '3. 23', 'new': '3. 19 '}, '000000': {'name': 'dongfeng Motors', 'open': '3. 96 ', 'new': '3. 86 '} };
Var openList = { '123': '9. 67 ', '123': '6. 82 ', '123': '3. 23 ', '000000': '3. 96' };
Var result = {}; Var I; // Obtain the data object of the open shard For (I in stocks ){ // Method 1 // Result [I] = stocks [I] ['open']; // Method 2 Result. I = stocks [I] ['open']; } |
Method 1 can obtain the expected result.
But the result obtained in method 2 is {I: "3.96 ″}.
Therefore, the object. attribute cannot be a variable. For example, I is overwritten by an attribute of the object.