An issue in which attribute names are quoted and unquoted when the object is declared by JS

In the case of a property name with quotation marks and no quotation marks are all possible, the effect is the same.

var obj = {      name    ' Hello ',      ' age '   : 1,  };     document.write (obj[' name '] + ' <br/> ' );  document.write (obj.age);  

The above two lines of code can be executed correctly.

When and only if your property name is an illegal and weird name, you will get an error.

var obj = {      333: ' This will be an    error '

document.write (obj.333);  

Error at this time.

var obj = {      "333": ' This will also be an error '  }; document.write (obj. 333);  

If the property name is a number, you must have double quotation marks and access with [] square brackets.

var obj = {    "333": ' This is correct '};console.log (obj["333"]);

Conclusion: Using the legal attribute name, using . and [] access are OK;

If the property name is a number, it must be surrounded by "" and accessed with [] square brackets.

An issue in which attribute names are quoted and unquoted when the object is declared by JS