properties of array object, if any. Thus it may be better to use a

traditional for loop with a numeric index when iterating over arrays.

• There are differences between the various Web browsers with regard to

which properties will be reflected with the for...in loop statement. In

theory, this is controlled by an internal state property defined by the

ECMAscript standard called "DontEnum", but in practice, each browser

returns a slightly different set of properties during introspection. It

(some_object.hasOwnProperty(property_name)) { ... }. Thus, adding a

function() {...} may cause for ... in loops to loop over the method's

name.

The syntax of the JavaScript while loop is as follows:

while (condition) {

statement1;

statement2;

statement3;

...

}

The syntax of the JavaScript do ... while loop is as follows:

do {

statement1;

statement2;

statement3;

...

} while (condition);

The with statement adds all of the given object's properties and methods

into the following block's scope, letting them be referenced as if they

were local variables.

with (document) {

const a = getElementById('a');

const b = getElementById('b');

const c = getElementById('c');

};

• Note the absence of document. before each getElementById() invocation.

The semantics are similar to the with statement of Pascal.

Because the availability of with statements hinders program performance

and is believed to reduce code clarity (since any given variable could

actually be a property from an enclosing with), this statement is not

allowed in strict mode.

JavaScript supports nested labels in most implementations. Loops or

blocks can be labeled for the break statement, and loops for continue.

Although goto is a reserved word,cite-ref-19[19] goto is not implemented in