Breaking out of a PrototypeJS .each() loop

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难免孤独
难免孤独 2021-02-05 09:52

In this very contrived example, I have an array with 3 elements that I\'m looping over using the .each() method.

var vals = $w(\'foo bar baz\'); 

vals.each( func         


        
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  •  遥遥无期
    2021-02-05 10:32

    Your are correct, and Prototype has created an object ($break) that can be thrown from the each-function to enable this functionality. According to the Prototype API docs:

    Regular loops can be short-circuited in JavaScript using the break and continue statements. However, when using iterator functions, your code is outside of the loop scope: the looping code happens behind the scene.

    In order to provide you with equivalent (albeit less optimal) functionality, Prototype provides two global exception objects, $break and $continue. Throwing these is equivalent to using the corresponding native statement in a vanilla loop. These exceptions are properly caught internally by the each method.

    Also, note that the $continue object has been deprecated, and to simulate a continue-statement, use a vanilla return statement instead.

    Code example:

    var result = [];
    $R(1,10).each(function(n) {
      if (0 == n % 2)
        return; // this equals continue
      if (n > 6)
        throw $break;
      result.push(n);
    });
    // result -> [1, 3, 5]
    

    You can read more about the each-function here: http://www.prototypejs.org/api/enumerable/each

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