Reducing Stack Use

The JavaScript stack is another resource that may be optimized. The default JavaScript stack size is just 4 KB on many embedded systems and seldom more than 8 KB. You can adjust the stack size in the creation section of your project's manifest. But, naturally, memory reserved for the stack is unavailable for other purposes. Eventually, you may need to optimize your stack use.

Each function call uses space on the stack, for function arguments, local variables, and the JavaScript stack frame. Eliminating nested function calls always helps. Sometimes those function calls are a bit hidden in JavaScript syntax. For example, this use of forEach adds two stack frames, one for the call to forEach and another to call the arrow function. Both can be eliminated at the cost of a local variable.

/* BEFORE */
let total = 0;
array.forEach(value => total += value)

/* AFTER */
let total = 0;
for (let i = 0; i < array.length; i++)
	total += array[i];

If your function exists by returning the value of another function, you can benefit from tail call optimizations (TCO). This eliminates the stack frame of the calling function before calling the final function. Normally, tail call optimizations are used to minimize the stack use of deep recursion. TCO is also an effective technique for eliminating unnecessary stack frames in non-recursive code.

// No tail call optimization
function negativeMin(a, b) {
	let c = Max.min(-a, -b);
	return c;
}

// Tail call optimization
function negativeMin(a, b) {
	return Max.min(-a, -b);
}

If you are unsure about your code's stack use, the xsbug debugger can help. Use the Instruments pane to monitor stack use. The value is updated in real-time as you step through the code.