A brief discussion on the difference between js object properties through dots (.) and square brackets ([])

[JS object attribute query and setting]

You can get the value of the attribute through the dot (.) or square bracket ([]) operator. The left side of the operator should be an expression that returns an object. For dots (.), the right-hand side must be a simple identifier named after the property name. For square brackets ([]), the square brackets must be an expression that evaluates to a string. This string is the name of the attribute:

<script type="text/javascript">
 var author = book.author; //得到book的"author"属性
 var name = author.subname; //得到author的"surname"属性
 var title = book["main title"]; //得到book的"main title"属性
</script>

When through dot operations (.) method object property, the property name is represented by an identifier. Identifiers must appear directly in the js program. They are not data types, so the program cannot modify them.

Conversely, when using [] to specify the properties of an object, the property name is represented by a string. Strings are the data type of js, and they can be modified and created while the program is running.

<script type="text/javascript">
 var addr = "";
 for(i=0;i<4;i++){
  addr += cutomer["address" + i] + "\n";
 }
</script>

This code reads the address0, adddress1, address2, adddress3 properties of the customer object and connects them.

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