Introducing seamless guesswork in JavaScript

Troy III 0 307 Views

Determine if a namespace/variable-name exists

Check for namespace existence in your environment variables and objects before writing to them.

Guess if "Book1.chapter22.paragraph37" exists without provoking errors and retrieve/send data if it exists with simplest JS expressions.

Call syntax:

isNS( [string], [num] );

Example:

 var nsresult =
 isNS( "Book1.chapter22.paragraph37", -1 ); 
 if( nsresult[0] ){ send( nsresult[1] ) else notify( nsresult[4], nsresult[2] ) };...

etc, etc.

Omit secondary argument (function-return modifier) to get a Boolean.
(Using 0, false, or undefined keyword has the same effect.)

 isNS( "myObject.property.subProperty.myMethod" );

_> Boolean : true/false

Modifier Possible values:
_> -1; (0|false|undefined); ( 1|true ); 2; 3 or 4.

Description:
(-1 ) _> returns array object containing complete inoculation.
( 0 ) _> optional; returns Boolean: true (if complete NS chain exist) : false (if it's broken).
( 1 ) _> if NS query exists, case true: returns the existing value; if not, case false: returns the last valid context if any, or the global object if root doesn't exist.
( 2 ) _> returns an array of existing namespaces in the argument query.
( 3 ) _> returns an array containing all specified namespaces.
( 4 ) _> returns the original query string.

*NS - stands for already familiar "Namespace" initials.
[This makes but a tinny cluster on some real A.I., Yet -a very important one!]

function isNS(arg,f) { /*b.b. Troy III p.a.e.*/
	if(typeof arg!="string") throw( 'TYPE_ERROR:"string required"');

	var i, a = arg.split("."), c = this, s = [], b, r;
	f = f || 0;
	
 	for( i in a ) {
		c ? a[i] in c ? ( c = c[ a[i] ], s.push( a[i] ), b = !0 ) : b = !1 : 0;
	}
 		r = [ b, c, s, a, arg ];
 		return f < 0 ? r : r[+f||f]; 
 };
Member Avatar for Troy III
Troy III 272 Posting Pro

Bump!
( serious coders have been sufferning for this for decades. Now that it's here it seems as if they've got used to getting a painful path around, accepting the fact that it doesn't exist. )

Member Avatar for Echo89
Echo89 9 Web Developer

If I understand what this function does, correctly, then surely I could just do the follwing instead? This causes no errors.

if(typeof someobject.someproperty !== "undefined") {
    // do something...
} else {
    // do something else...
}
Member Avatar for stbuchok
stbuchok

echo89, what about this:

if(typeof someobject.someobj.someproperty !== "undefined") {
    // do something...
} else {
    // do something else...
}

what happens if someobject is undefined?

Member Avatar for Echo89
Echo89 9 Web Developer

Stbuchok, I could do type of for each variable/property in nested if blocks, but that is rather tedious. I can see the use of this function now.

Member Avatar for Troy III
Troy III 272 Posting Pro

There are other critical uses also.

Say, checking for an explicit "undefined" value of a named property.
Checking if a variable name is already declared but (still) not initialized.
Or, that there is an object member whose value is still waiting to be assigned a value etc.

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