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Create 3D dimensional array

In Javascript, I don't see any tutorials clearly explain how to create like
MyItems[Row][Index][categories]
so that
MyItems[0][0][0]=1
MyItems[1][0][0]='stock'
MyItems[5][1][0]='pending'
My use case is each Index will contain different value which is integer or string.
What is the best way to avoid error when accessing MyItems[0][1][0] that has no value?

Because JS doesn't have actual multidimensional arrays, but instead merely have nested arrays that don't necessarily form a rectangular structure, you'd need to check for each nested array first. A simple "truthy" test would be fine.
if (myItems[0] && myItems[0][0])
myItems[0][0].push(1);
If you wanted to create the arrays that aren't there, then you can do that like this:
if (!myItems[0])
myItems[0] = [];
if (!myItems[0][0])
myItems[0][0] = [];
myItems[0][0].push(1);
Of course this assumes that the first and second levels should always be arrays, and only the third level will hold the actual values. You'll need to adjust it if that's not the case.
Also, a function would be a good idea to get rid of the repetition.
function addNested(outer, idx1, idx2, idx3, value) {
if (!outer[idx1])
outer[idx1] = [];
if (!outer[idx1][idx2])
outer[idx1][idx2] = [];
outer[idx1][idx2][idx3] = value;
}
addNested(myItems, 1, 0, 0, 'stock');

This is how you'd make a 3D array, but I'd recommend against mixing data types in your array, that's not exactly a common or standard practice.
// just filler stuff, ignore the body of this function
function getStringOrNumber(row, col, cat) {
var thing = row * cols * cats + col * cats + cat;
return Math.random() < .5 ? thing : thing.toString();
}
// something to deal with each value
function doSomething(value) {
switch (typeof value) {
case 'string':
// logic for string type
break;
case 'number':
// logic for number type
break;
default:
// unexpected?
break;
}
}
// here's how you make your 3D array
var rows = 10,
cols = 10,
cats = 10,
array3d = new Array(rows),
i, j, k;
for (i = 0; i < rows; i++) {
array3d[i] = new Array(cols);
for (j = 0; j < cols; j++) {
array3d[i][j] = new Array(cats);
for (k = 0; k < cats; k++) {
array3d[i][j][k] = getStringOrNumber(i, j, k);
doSomething(array3d[i][j][k]);
}
}
}
If you want to check whether an index exists on the 3d array, try a function like this:
function setValue(array3d, row, col, cat, value) {
if (array3d[row] && array3d[row][col] && array3d[row][col][cat]) {
array3d[row][col][cat] = value;
} else {
throw new RangeError("Indices out of range");
}
}

If you were to allocate each array at each index in a breadth-first pattern before accessing any of it, then this would work without any special handling.
However, as you've correctly recognized, if you want to be able to access indexes that may not have been allocated yet, this won't work.
Actually, to be more specific, you are allowed to attempt to read an index outside the length of an array, in which case you'll get undefined. The problem is that if you get undefined for the first or second depth, then an attempt to index that undefined value will fail.
Thus, to prevent this error, you must guard against undefined first- or second-depth indexes.
The best way to do this is to write a class that provides a getter and setter that automatically take care of the special handling requirements. Here's an example of such a class, defined using the prototype pattern:
(function() {
var Array3D = function() {
this.data = [];
};
Array3D.prototype.get = function(r,c,z) {
if (this.data.length <= r) return undefined;
if (this.data[r].length <= c) return undefined;
return this.data[r][c][z];
};
Array3D.prototype.set = function(r,c,z,v) {
if (this.data.length <= r) this.data[r] = [];
if (this.data[r].length <= c) this.data[r][c] = [];
this.data[r][c][z] = v;
return this;
};
window.Array3D = Array3D;
})();
var a = new Array3D();
alert(a.get(0,0,0)); // undefined, no error
a.set(0,0,0,'x');
alert(a.get(0,0,0)); // 'x'
a.set(234,1234,342,'y');
alert(a.get(234,1234,342)); // 'y'
alert(a.get(0,1,0)); // undefined, no error
alert(a.get(12341234,243787,234234)); // undefined, no error

Since this completely differs from my other answer, I thought it would be helpful to suggest another approach using nested sparse arrays which could be implemented using associative arrays or objects. Try this:
// N-dimensional array
function ArrayND() {
// nothing to do here, seriously
}
ArrayND.prototype.setValue = function (value) {
var indices = arguments,
nest = this,
index, i;
// note the range of values since the last recursion is being set to a value
for (i = 1; i < indices.length - 2; i++) {
index = indices[i];
if (nest[index] instanceof ArrayND) {
nest = nest[index];
} else if (typeof nest[index] === "undefined") {
// recursive functionality!
nest = nest[index] = new ArrayND();
} else {
// we don't want to get rid of this value by accident!
return false;
}
}
// now "nest" is equal to the ArrayND you want to set the value inside of
index = indices[i];
nest[index] = value;
// we set the value successfully!
return true;
}
ArrayND.prototype.getValue = function () {
var indices = arguments,
nest = this,
index, i;
// note the range because we're getting the last value
for (i = 0; i < indices.length; i++) {
index = indices[i];
// for last recursion, just has to exist, not be ArrayND
if (nest[index]) {
nest = nest[index];
} else {
// nothing is defined where you're trying to access
return undefined;
}
}
return nest;
}
var arrayND = new ArrayND();
arrayND.setValue(1, 0, 0, 0);
arrayND.setValue("stock", 1, 0, 0);
arrayND.setValue("pending", 5, 1, 0);
// you can treat it like a normal 3D array if you want
console.log(arrayND[0][0][0]); // 1
console.log(arrayND[1][0][0]); // "stock"
console.log(arrayND[5][1][0]); // "pending"
// or use a nicer way to get the values
console.log(arrayND.getValue(1, 0, 0)); // "stock"
// phew, no errors!
console.log(arrayND.getValue(3, 1, 0)); // undefined
// some awesome recursive functionality!
console.log(arrayND.getValue(5).getValue(1).getValue(0)); // "pending"

Check for continuous order in array in javascript

var userInput = prompt('enter number here');
var number = new Array(userInput.toString().split(''));
if (number ????){ //checks if the number is in a continuous stream
alert(correct);
}
else{
alert(invalid);
}
In Javascript, what can I do at "????" to check if it is in a continuous order/stream? Also how can I do this so that it only checks for this order/stream after a specific index in the array? Meaning the user enters say "12345678901234" which would pop up correct, but "12347678901234" would pop up invalid?(note there are two 7's) For the second part "3312345678901234" would pop up correct, how can this be implemented?

You can make a function that checks any string for a stream of continuous/increasing alpha-numeric characters starting at a given index like this:
function checkContinuous(str, startIndex) {
startindex = startIndex || 0;
if (str.length <= startIndex) {
return false;
}
var last = str.charCodeAt(startIndex);
for (var i = startIndex + 1; i < str.length; i++) {
++last;
if (str.charCodeAt(i) !== last) {
return false;
}
}
return true;
}
If it's numbers only and wrapping from 9 back to 0 is considered continuous, then it's a little more complicated like this:
function checkContinuous(str, startIndex) {
// make sure startIndex is set to zero if not passed in
startIndex = startIndex || 0;
// skip chars before startIndex
str = str.substr(startIndex);
// string must be at least 2 chars long and must be all numbers
if (str.length < 2 || !/^\d+$/.test(str)) {
return false;
}
// get first char code in string
var last = str.charCodeAt(0);
// for the rest of the string, compare to last code
for (var i = 1; i < str.length; i++) {
// increment last charCode so we can compare to sequence
if (last === 57) {
// if 9, wrap back to 0
last = 48;
} else {
// else just increment
++last;
}
// if we find one char out of sequence, then it's not continuous so return false
if (str.charCodeAt(i) !== last) {
return false;
}
}
// everything was continuous
return true;
}
Working demo: http://jsfiddle.net/jfriend00/rHH4B/

No need for arrays, just back though the string one character at a time.
When you hit a 0, substitute 10, and continue until the number
is not one more than the previous one.
function continuousFromChar(str, start){
start= start || 0;
var i= 0, L= str.length, prev;
while(L){
c= +(str.charAt(-- L)) || 10; // use 10 for 0
prev=+(str.charAt(L- 1));
if(c-prev !== 1) break;
}
return start>=L;
}
var s= "3312345678901234";
continuousFromChar(s,2)
/* returned value: (Boolean)
true
*/

This will do the checking in real-time entry, but a similar principle could be used to check an entry on a button submit or similar. I was not 100% sure as to which way you wanted it, so I went for the live method.
HTML
<input id="stream" type="text" />
Javascript
window.addEventListener("load", function () {
document.getElementById("stream").addEventListener("keyup", function (evt) {
var target = evt.target;
var value = target.value;
var prev;
var last;
var expect;
target.value = value.replace(/[^\d]/, "");
if (value.length > 1) {
prev = parseInt(value.slice(-2, -1), 10);
last = parseInt(value.slice(-1), 10);
expect = prev + 1;
if (expect > 9) {
expect = 0;
}
if (last !== expect) {
target.value = value.slice(0, value.length - 1);
}
}
}, false);
});
On jsfiddle
By changing the value here
if (value.length > 1) {
You can change where the checking starts.
Update: Ok, so it is function that you want, and you insist that it splits the string into an array. Then using the above as a reference, you could convert it to something like this.
Javascript
window.addEventListener("load", function () {
var testStrings = [
"0123456789012",
"0123456789",
"0123455555",
"555012345678901234",
"0123455555"];
function test(string, offset) {
if (typeof string !== "string" || /[^\d]/.test(string)) {
return false;
}
var array = string.split("");
var prev;
var last;
var expect;
return !array.some(function (digit, index) {
if (index >= offset) {
prev = parseInt(array[index - 1], 10);
last = parseInt(digit, 10);
expect = prev + 1;
if (expect > 9) {
expect = 0;
}
if (last !== expect) {
return true;
}
}
return false;
});
}
testStrings.forEach(function (string) {
console.log(string, test(string, 1));
});
});
On jsfiddle
As your question does not fully specify all possibilities, the above will return true for an empty string (""), of course you can simply add a check at the very beginning for that.
I also do not perform any checking for a valid number for your offset, but again this is something simple that you can add.
Of course these are just one (two) of many possible solutions, but hopefully it will set your mind in the right direction of thought.

There are some good answers here, but I would like to show a slight variation. I think it is important to showcase some different aspects of JavaScript and separating interests in code.
Functions as first class objects are cool - the exact rules for "continuous" can be changed with only changing the predicate function. Perhaps we should allow skipping numbers? No problem. Perhaps we allow hex digits? No problem. Just change the appropriate follows function for the specific rules.
This can be implemented generically because strings support indexing. This will work just as well over other array-like objects with an appropriate follows function. Note that there are no string-specific functions used in the continuous function.
Code also on jsfiddle:
// returns true only iff b "follows" a; this can be changed
function follows_1Through9WithWrappingTo0(b,a) {
if (b === "1" && a === undefined) {
// start of sequence
return true;
} else if (b === "0" && a === "9") {
// wrap
return true;
} else {
// or whatever
return (+b) === (+a) + 1;
}
}
function continuous(seq, accordingTo, from) {
// strings can be treated like arrays; this code really doesn't care
// and could work with arbitrary array-like objects
var i = from || 0;
if ((seq.length - i) < 1) {
return true;
}
var a = undefined;
var b = undefined;
for (; i < seq.length; i++) {
b = seq[i];
if (!accordingTo(b, a)) {
return false; // not continuous
}
a = b;
}
return true;
}
function assert(label, expr, value) {
if (!(expr === value)) {
alert("FAILED: " + label);
}
}
var follows = follows_1Through9WithWrappingTo0;
assert("empty1", continuous("", follows), true);
assert("empty2", continuous("foobar", follows, 6), true);
assert("skip", continuous("331234", follows, 2), true);
assert("good 1", continuous("123456789", follows), true);
assert("good 2", continuous("12345678901234", follows), true);
assert("bad seq 1", continuous("12347678901234", follows), false);
assert("bad seq 2", continuous("10", follows), false);
// here a different predicate ensures all the elements are the same
var areAllSame = function (b, a) {
return a === undefined || a === b;
};
assert("same", continuous("aaaaa", areAllSame), true);
Note that the skipping could also be extracted out of the continuous function: in a language with better "functional" collection support, such as C#, this is exactly what I'd do first.

Insert a line into a function in JavaScript

In JavaScript, is it possible to insert a line into a function that already exists? I want to create a function that inserts a line at a specific position in a function:
function insertLine(theFunction, lineToInsert, positionToInsert){
//insert a line into the function after the specified line number
}
For example, would it be possible to programmatically insert the line checkParameterTypes(min, "string", max, "string"); before the first line of this function?
function getRandomInteger(min, max) {
return Math.floor(Math.random() * (max - min + 1)) + min;
}

If you want something to happen at the beginning of a function, you can use the following. You do have access to this and the arguments from your injected function. So it will still work for functions that require a specific context.
function inject(before, fn) {
return function(){
before.apply(this, arguments);
return fn.apply (this, arguments);
}
}
For example
function add(a, b) {
return a + b;
}
function concat(a, b) {
return a + b;
}
/**
* You can repeat index and type to check multiple arguments
*/
function createArgumentChecker(index, type /**index, type, ... */) {
var originalArgs = arguments;
return function() {
for (var i=0; i < originalArgs.length; i+=2) {
var index = originalArgs[i],
requestedType = originalArgs[i+1],
actualType = typeof arguments[index];
if (typeAtIndex != actualType) {
console.log("Invalid argument passed at index " + index +
". Expected type " + requestedType + "but it's " + actualType );
}
}
}
}
function logArguments() {
console.log(this, arguments);
}
// Inject an argument checker
add = inject(add, createArgumentChecker(0,"number", 1, "number"));
concat = inject (concat, createArgumentChecker(0, "string", 1, "string"));
// You can even do it multiple times, inject an argument logger;
add = inject(add, logArguments);
concat = inject(concat, logArguments);
JSfiddle
This can be handy when debugging websites that you can't modify the source code, I wouldn't use it do parameter checking unless you can strip it our for the production version.

Yes you can but using eval is always evil ;)
function insertInbetween (arr, value, index) {
var inserted, i, newarr = [];
for (i = 0; i < arr.length; i++) {
if(i == index && !inserted) {
newarr[i] = value;
inserted = true;
}
newarr.push(arr[i]);
}
return newarr;
}
function test (a, b) {
console.log(a,b);
}
var fstrarr = test.toString().split('\n');
eval(insertInbetween(fstrarr, "console.log('injected!');", 1).join('\n'));
Edit:
As mentioned in the comments to your question you'll loose scope by doing so.

How can I use array variable in an if statement?

var n = new Array();
n[0] = "zero";
n[1] = "first";
n[2] = "second"
function myFunction() {
var x = prompt("Question?")
if (x.toLowerCase() == n) {
//code
} else {
//code
}
}
Is it possible to make it so that if any of the array variables are typed in, the if / else function is still carried out.

I'm guessing you want to check if the typed value exists in the array? If so:
function myFunction() {
var x = prompt("Question?")
if (n.indexOf(x.toLowerCase()) > -1) {
//code
} else {
//code
}
}
You you need to support IE8 and earlier, you'll need a shim for Array.prototype.indexOf (for example, the one provided by MDN).

Depending on if you want the condition to be true on every array element or just on at least one, you can use n.every or n.some.

var n = new Array();
n[0] = "zero";
n[1] = "first";
n[2] = "second"
function myFunction()
{
var x=prompt("Question?")
for (var i in n) {
if (x.toLowerCase() === n[i] ){ alert("true"); }
}
}
myFunction();

How to parse pure functions

Let's say you have the following function
var action = (function () {
var a = 42;
var b = 2;
function action(c) {
return a + 4 * b + c;
}
return action;
}());
// how would you parse action into it's serialized LISP / AST format?
var parsed = parse(action);
Is it possible to have a function that takes a reference to the function action and outputs say the LISP format (lambda (c) (plus (plus 42 (multiply 4 2)) c))
We're allowed to put some restrictions on what action can be.
the body should only be a single expression
it should be a pure function
any free variables are constants
The main question is given a function you can invoke with a range of inputs and it's source code can you discover the correct value to substitute the free variables with?
For the above example you know that a and b are constant and you could intellectually plot the output for a few values and see the pattern and then just know what the constants are.
Question:
How would you write a function that takes a function reference and it's source code and produces some form of AST for the function with any free variables substituted for their run-time values.
An example of an AST format would be the LISP equivalent of the code.
I basically want to serialize and deserialize the function and have it behave the same
It should be noted that the problem becomes trivial if you pass { a: a, b: b } to the analysis function. That would be cheating.
Use-case:
I want to generate a language agnostic form of a pure JavaScript function so I can effectively pass it to C++ without requiring the user of my library to use a DSL to create this function
Let's imagine you had a database driver
var cursor = db.table("my-table").map(function (row) {
return ["foo", row.foo]
})
You want to determine at run-time what the function is and convert it into an AST format so that you can use your efficient query builder to convert it into SQL or whatever query engine your database has.
This means you don't have to write:
var cursor = db.table("my-table").map(function (rowQueryObject) {
return db.createArray(db.StringConstant("foo"), rowQueryObject.getProperty("foo"))
})
Which is a function the DB library can execute with a query object and have you build the query object transformation without verbose methods.

Here is a full solution (using catalog of variables which is accessible by the parse function):
var CONSTANTS = {
a: 42,
b: 2,
c: 4
};
function test() {
return a + 4 * b + c;
}
function getReturnStatement(func) {
var funcStr = func.toString();
return (/return\s+(.*?);/g).exec(funcStr)[1];
}
function replaceVariables(expr) {
var current = '';
for (var i = 0; i < expr.length; i += 1) {
while (/[a-zA-Z_$]/.test(expr[i]) && i < expr.length) {
current += expr[i];
i += 1;
}
if (isNumber(CONSTANTS[current])) {
expr = expr.replace(current, CONSTANTS[current]);
}
current = '';
}
return expr;
}
function isNumber(arg) {
return !isNaN(parseInt(arg, 10));
}
function tokenize(expr) {
var tokens = [];
for (var i = 0; i < expr.length; i += 1) {
if (isWhitespace(expr[i])) {
continue;
} else if (isOperator(expr[i])) {
tokens.push({
type: 'operator',
value: expr[i]
});
} else if (isParentheses(expr[i])) {
tokens.push({
type: 'parant',
value: expr[i]
});
} else {
var num = '';
while (isNumber(expr[i]) && i < expr.length) {
num += expr[i];
i += 1;
}
i -= 1;
tokens.push({
type: 'number',
value: parseInt(num, 10)
});
}
}
return tokens;
}
function toPrefix(tokens) {
var operandStack = [],
operatorStack = [],
current,
top = function (stack) {
if (stack) {
return stack[stack.length - 1];
}
return undefined;
};
while (tokens.length) {
current = tokens.pop();
if (current.type === 'number') {
operandStack.push(current);
} else if (current.value === '(' ||
!operatorStack.length ||
(getPrecendence(current.value) >
getPrecendence(top(operatorStack).value))) {
operatorStack.push(current);
} else if (current.value === ')') {
while (top(operatorStack).value !== '(') {
var tempOperator = operatorStack.pop(),
right = operandStack.pop(),
left = operandStack.pop();
operandStack.push(tempOperator, left, right);
}
operatorStack.pop();
} else if (getPrecendence(current.value) <=
getPrecendence(top(operatorStack).value)) {
while (operatorStack.length &&
getPrecendence(current.value) <=
getPrecendence(top(operatorStack).value)) {
tempOperator = operatorStack.pop();
right = operandStack.pop();
left = operandStack.pop();
operandStack.push(tempOperator, left, right);
}
}
}
while (operatorStack.length) {
tempOperator = operatorStack.pop();
right = operandStack.pop();
left = operandStack.pop();
operandStack.push(tempOperator, left, right);
}
return operandStack;
}
function isWhitespace(arg) {
return (/^\s$/).test(arg);
}
function isOperator(arg) {
return (/^[*+\/-]$/).test(arg);
}
function isParentheses(arg) {
return (/^[)(]$/).test(arg);
}
function getPrecendence(operator) {
console.log(operator);
switch (operator) {
case '*':
return 4;
case '/':
return 4;
case '+':
return 2;
case '-':
return 2;
default:
return undefined;
}
}
function getLispString(tokens) {
var result = '';
tokens.forEach(function (e) {
if (e)
switch (e.type) {
case 'number':
result += e.value;
break;
case 'parant':
result += e.value;
break;
case 'operator':
result += getOperator(e.value);
break;
default:
break;
}
result += ' ';
});
return result;
}
function getOperator(operator) {
switch (operator) {
case '+':
return 'plus';
case '*':
return 'multiplicate';
case '-':
return 'minus';
case '\\':
return 'divide';
default:
return undefined;
}
}
var res = getReturnStatement(test);
console.log(res);
res = replaceVariables(res);
console.log(res);
var tokens = tokenize(res);
console.log(tokens);
var prefix = toPrefix(tokens);
console.log(prefix);
console.log(getLispString(prefix));
I just wrote it so there might be some problems in the style but I think that the idea is clear.
You can get the function body by using the .toString method. After that you can use regular expression to match the return statement
(/return\s+(.*?);/g).exec(funcStr)[1];
Note that here you must use semicolons for successful match! In the next step all variables are transformed to number values using the CONSTANTS object (I see that you have some parameters left so you may need little modifications here). After that the string is being tokenized, for easier parsing. In next step the infix expression is transformed into a prefix one. At the last step I build a string which will make the output looks like what you need (+ - plus, - - minus and so on).

Since I'm not sure you're able to get the method's body after having invoked it, here is an alternative solution:
var a = 42;
var b = 2;
function action(c) {
return a + 4 * b + c;
}
/**
* get the given func body
* after having replaced any available var from the given scope
* by its *real* value
*/
function getFunctionBody(func, scope) {
// get the method body
var body = func.toString().replace(/^.*?{\s*((.|[\r\n])*?)\s*}.*?$/igm, "$1");
var matches = body.match(/[a-z][a-z0-9]*/igm);
// for each potential var
for(var i=0; i<matches.length; i++) {
var potentialVar = matches[i];
var scopedValue = scope[potentialVar];
// if the given scope has the var defined
if(typeof scopedValue !== "undefined") {
// add "..." for strings
if(typeof scopedValue === "string") {
scopedValue = '"' + scopedValue + '"';
}
// replace the var by its scoped value
var regex = new RegExp("([^a-z0-9]+|^)" + potentialVar + "([^a-z0-9]+|$)", "igm");
var replacement = "$1" + scopedValue + "$2";
body = body.replace(regex, replacement);
}
}
return body;
}
// calling
var actionBody = getFunctionBody(action, this);
// log
alert(actionBody);
Prints:
return 42 + 4 * 2 + c;
DEMO
You would then have to implement your own function toLISP(body) or any function else you may need.
Note that it won't work for complex scoped variables such as var a = {foo: "bar"}.