How to stop append string in forEach? - node.js

Question

Here is what I got:
I try to send requests to a service, that's what otherFunction() do. Each request use different parameters loaded from config.events. Then I want to append a randomParam to each event.
config = { events: [...] }
for(let i = 0; i < 100; i++){
config.events.forEach(element => {
// Get a random string
str = '&randomParam=' + Random.word(10)
element.url += str
console.log(element.url)
otherFunction(element)
// the element.url keep append random word 100 times, but I expect only one word append for each loop
})
}
I'd trid create a const var, using deep copy (JSON parse/stringify) and delete element.url and add it again. But none of it could solve my problem.
Actually, I did not know what exactly happend in my code and how this caused.
Current Result:
https://example.com/exampleApi/index.html?testParam=123&randomParam=rbveostvie
https://example.com/exampleApi/index.html?testParam=123&randomParam=rbveostvie&randomParam=bjanckrbjc
https://example.com/exampleApi/index.html?testParam=123&randomParam=rbveostvie&randomParam=bjanckrbjc&randomParam=rbuunvtdux
Expect Result:
https://example.com/exampleApi/index.html?testParam=123&randomParam=rbveostvie
https://example.com/exampleApi/index.html?testParam=123&randomParam=bjanckrbjc
https://example.com/exampleApi/index.html?testParam=123&randomParam=rbuunvtdux

Answer 1

You need to move the random string assignment out of the inner forEach loop.
var config = {
events: [
{
url: "foo"
},
{
url: "baz"
}
]
};
for (let i = 0; i < 100; i++) {
var str = "&randomParam=" + Random.word(10);
config.events.forEach(element => {
otherFunction(Object.assign({}, element, { url: element.url + str }));
});
}
For each i out of n=100 iterations, your inner forEach loop would iterate k=config.events.length times. By moving the random string outside the inner forEach loop, you would ensure that you generate n random strings instead of n * k random strings.
Edit
As per OP updated description, the actual problem is that element.url is being mutated. On every iteration, it will append the random string to the previously set url. Hence, I have updated my answer to include Object.assign({}, element, { url: element.url + str }) which will make sure no object in config.events gets mutated.
Please see below a working example:
function getRandomString() {
return Math.random()
.toString(36)
.substring(7);
}
var config = {
events: [{
url: "foo"
},
{
url: "baz"
}
]
};
function otherFunction(element) {
console.info(element.url);
}
for (let i = 0; i < 5; i++) {
var str = "&randomParam=" + getRandomString();
config.events.forEach(element => {
otherFunction(Object.assign({}, element, {
url: element.url + str
}));
});
}

Answer 2

I assume that config.events is an array of 100 elements, and you want to add a random string to every element.url.
You don't need two loops, one is enough. Remove that outer loop, and you'll get what you want
--EDIT--
According to the comment the author posted later, the outer loop should be moved to wrap the otherFunction call.
config = { events: [...] }
config.events.forEach(element => {
// Get a random string
str = '&randomParam=' + Random.word(10)
element.url += str
for(let i = 0; i < 100; i++){
otherFunction(element)
}
})