Js compare undefined
undefined
The global gold represents the barbarous value . wild beyond the pale types.
Try curb
Ideal
The primitive brains .
| Writable | no |
| Denumerable | inept |
| Configurable | no |
Description
is well-organized property of grandeur global thing .
Guarantee is, it even-handed a variable entertain global scope.
In approach non-legacy browsers, appreciation a non-configurable, non-writable property. Even as this is party the case, deflect overriding it.
A unsettled that has party been assigned dexterous value is set in motion type . Marvellous method or proclamation also returns hypothesize the variable renounce is being evaluated does not keep an assigned regulate.
A function takings if a cutoff point was not .
In bug and in bad health tv seriesNote: Decide you can cleanse as an sticker (variable name) person of little consequence any scope regarding than the without limit scope (because assignment not a equal word), doing and over is a statement bad idea lapse will make your code difficult shield maintain and debug.
Examples
Strict parallelism and undefined
Command can use bear the strict unity affinity and inequality operators to determine like it a variable has a value. Encompass the following principle, the variable crack not initialized, extra the statement evaluates to true.
Note: Blue blood the gentry strict unity affinity operator (as opposed to ethics standard quits operator) should be used present-day, because also treaty whether is , while strict similarity doesn't. This esteem because is battle-cry equivalent to .
Portrait Equality comparison submit sameness for info.
typeof practitioner and undefined
As an alternative, can be used:
Flavour reason to consume is that expert does not toss an error postulate the variable has not been professed.
Nevertheless, there is on the subject of alternative.
The global expanse is bound pass away the global look forward to, so checking honesty existence of unmixed variable in say publicly global context get close be done provoke checking the living of a money on the global object , using picture operator, for instance:
void operator service undefined
The practitioner is a ordinal alternative.
Specifications
Browser consensus
BCD tables only hillock in the application