JavaScript Function Test if Variable is Null, is an Array and Proper Array Length

JavaScript Function Test if Variable is Null, is an Array and Proper Array Length ALL at the Same Time

If [arr] is multidimensional then you can pass any depth or level of the array to the function. For example, for a regular, single dimension array that you want to test has 4 elements ...

const [myArrayOK, myArrayLength] = isArrayProperLength(myArray, 4); if(myArrayOK){ console.log("ERROR: [myArrayOK] is " + myArrayLength + " length"); return false; }

If you have a 2 part array and you want to test the second level of the array ...

const [myArrayOK, myArrayLength] = isArrayProperLength(myArray[0], 4); if(myArrayOK){ console.log("ERROR: [myArrayOK] is " + myArrayLength + " length"); return false; } /* ------------------------------------------------------------- test if variable [arr] is an array and if length [expectedLength] is the expected length of the array. simutaneously tests if [arr] is null as if so, function returns false with console log error "ERROR: [arr] is not an array [function isArrayProperLength]" return: 2 part array [0] true or false [1] length of the array -------------------------------------------------------------- */ function isArrayProperLength(arr, expectedLength) { // built in js function to test if variable is // array but also returns false if [arr] is null if(!Array.isArray(arr)){ console.log("ERROR: [arr] is not an array [function isArrayProperLength]"); return [false, null]; } // if we get here we know [arr] is both not null and // and is array, this tests for proper length of [arr] if(arr.length !== expectedLength){ console.log("ERROR: [arr] is a " + arr.length + " part array, not " + expectedLength + " part array [function isArrayProperLength]"); return [false, arr.length]; } return [true, arr.length]; }