EDIT 2: Why has this very specific question been marked as a duplicate of this very conceptual one: What's the difference between passing by reference vs. passing by value?. If someone else had the same question as me, they wouldn't end up with this one on Google by searching for it and - even if they did - it wouldn't answer their question.
EDIT: Thanks everyone for your help so far. Pretty difficult stuff to understand from my point of view. The reason I'm doing this is that I've set up a function which I'm calling multiple times and in which I define a variable (a unique one with each call). I need to be able to refer back to each unique variable afterwards. Here is my actual attempted code below. What would the right way to do this be?
let newSeq1
let newSeq2
function sequenceClip(sample, length, sequenceVariable) {
let currentPosition = Tone.Transport.position
let whenToStart
if (currentPosition === '0:0:0') {
whenToStart = '0:0:0'
} else {
const barToStartOn = +currentPosition.slice(0, currentPosition.indexOf(':'))
whenToStart = `${barToStartOn + 1}:0:0`
}
sequenceVariable = new Tone.Sequence((time, note) => {
sampler.triggerAttackRelease(note, '4m', time)
}, [sample], length).start(whenToStart);
}
loop1.addEventListener('mousedown', () => {
sequenceClip("C3", '1m', newSeq1)
})
loop2.addEventListener('mousedown', () => {
sequenceClip("C#3", '4m', newSeq2)
})
How do I pass a variable into a function in Javascript to be assigned a value. E.g.:
Why does the variable not get assigned the value 5? And what's the way around this?
let a
function defineVariable(var2beDefined) {
var2beDefined = 5
}
defineVariable(a)
console.log(a === 5)Reassigning an identifier, by itself, never has any side-effects (in most circumstances) - the only change resulting from someIdentifier = someNewValue will be when other parts of the code reference that same someIdentifier.
If you want to pass in something to be assigned to, pass in a function which, when called, assigns to the outer variable.
let a;
function defineVariable(callback) {
callback(5);
}
defineVariable(newVal => a = newVal);
console.log(a === 5)The only time that assigning to an identifier will have side effects is if:
arguments object will be changed as well)You would typically write an initializer function that returns a value and assign that return value to the relevant global variable. For example:
let newSeq1
let newSeq2
function sequenceClip(sample, length, sequenceVariable) {
let currentPosition = Tone.Transport.position
let whenToStart
if (currentPosition === '0:0:0') {
whenToStart = '0:0:0'
} else {
const barToStartOn = +currentPosition.slice(0, currentPosition.indexOf(':'))
whenToStart = `${barToStartOn + 1}:0:0`
}
return new Tone.Sequence((time, note) => {
sampler.triggerAttackRelease(note, '4m', time)
}, [sample], length).start(whenToStart);
}
loop1.addEventListener('mousedown', () => {
newSeq1 = sequenceClip("C3", '1m')
})
loop2.addEventListener('mousedown', () => {
newSeq2 = sequenceClip("C#3", '4m')
})
Note that both newSeq1 and newSeq2 will be undefined until the first mousedown/mouseup events.