continue in cursor forEach

Question

I m building an app using meteor js and MongoDB and I have a question about cursor forEach    I want to check some conditions in the beginning of each forEach iteration and then skip the element if I don t have to do the operation on it so I can save some time   Here is my code      Fetch all objects in SomeElements collection var elementsCollection   SomeElements find    elementsCollection forEach function element     if  element shouldBeProcessed    false          Here I would like to continue to the next element if this one         doesn t have to be processed    else         This part should be avoided if not neccessary     doSomeLengthyOperation              I know I could turn cursor to array using cursor find   fetch   and then use regular for-loop to iterate over elements and use continue and break normally but I m interested if there is something similiar to use in forEach

User · Answer

In my opinion the best approach to achieve this by using the filter method as it's meaningless to return in a forEach block; for an example on your snippet:

// Fetch all objects in SomeElements collection
var elementsCollection = SomeElements.find();
elementsCollection
.filter(function(element) {
  return element.shouldBeProcessed;
})
.forEach(function(element){
  doSomeLengthyOperation();
});

This will narrow down your elementsCollection and just keep the filtred elements that should be processed.

User · Answer

Here is a solution using for of and continue instead of forEach    let elementsCollection   SomeElements find     for  let el of elementsCollection            continue will exit out of the current         iteration and continue on to the next     if   el shouldBeProcessed           continue             doSomeLengthyOperation           This may be a bit more useful if you need to use asynchronous functions inside your loop which do not work inside forEach  For example     async fuction     for  let el of elementsCollection         if   el shouldBeProcessed           continue             let res       try           res   await doSomeLengthyAsyncOperation          catch  err            return Promise reject err

User · Answer

Each iteration of the forEach   will call the function that you have supplied  To stop further processing within any given iteration  and continue with the next item  you just have to return from the function at the appropriate point   elementsCollection forEach function element     if   element shouldBeProcessed      return     stop processing this iteration       This part will be avoided if not neccessary   doSomeLengthyOperation

User · Answer

Use continue statement instead of return to skip an iteration in JS loops

User · Answer

Making use of JavaScripts short-circuit evaluation  If el shouldBeProcessed returns true  doSomeLengthyOperation  elementsCollection forEach  el   gt     el shouldBeProcessed  amp  amp  doSomeLengthyOperation

[javascript] "continue" in cursor.forEach()

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