使用点符号和空格访问对象键

Question

I came across the following:

var object = {};
object.name = 'ABC';
console.log(object.     name); // this is still valid

Notice the space after object.

Why is this valid? Is there any ECMA specification for this?

Same is true for all the inherited properties for different data types.

I've tested this on a node terminal.

Thanks!

Answer 1

Why is this valid?

Because whitespace is largely (though not entirely) irrelevant in the JavaScript syntax. You can safely insert any whitespace other than a line break between two tokens (and in most, but not all cases, you can insert line breaks as well; the "most" is due to ASI ). You can't insert spaces within tokens (because it breaks them up into two tokens), but you can between tokens.

As Federico klez Culloca points out ( link ), . is an operator, just like + or * . The fact we generally don't put spaces around it, but do put spaces around them, is simply convention.

These are all valid:

console.log(object.name);
console.log(
    object.name
);
console.log(
    object . name
);
console.log(
    object
    .
    name
);

Is there any ECMA specification for this?

Of course, the specification itself . Specifically here and here . From that last link:

Input elements other than white space and comments form the terminal symbols for the syntactic grammar for ECMAScript and are called ECMAScript tokens. These tokens are the reserved words, identifiers, literals, and punctuators of the ECMAScript language. Moreover, line terminators, although not considered to be tokens, also become part of the stream of input elements and guide the process of automatic semicolon insertion (11.9). Simple white space and single-line comments are discarded and do not appear in the stream of input elements for the syntactic grammar.