In situations where you need to traverse nested data structures recursively and execute an operation for each element, you might use a combination of recursion and forEach. However, there may be instances where you need to prematurely exit the forEach loop.
Unlike a regular loop with break or continue statements, forEach lacks a built-in mechanism to halt its iteration. To simulate this behavior, let's explore three approaches:
1. The "Ugly" Way: Using a Contextual Boolean
Pass a second argument to forEach as the context and store a boolean value in it. Inside the callback function, check the boolean and break out if necessary. This approach is visually unappealing.
<code class="javascript">function recurs(comment) {
var stop = false;
comment.comments.forEach(function (elem) {
recurs(elem);
if (...) stop = true;
}, stop);
}</code>2. The "Controversial" Way: Exception Handling
Enclose the forEach loop within a try-catch block. When you want to break, throw an exception and catch it outside the loop. This approach can impact performance and may raise concerns about code readability.
<code class="javascript">try {
comment.comments.forEach(function (elem) {
recurs(elem);
if (...) throw new Error("Stop Iteration");
});
} catch (e) {
if (e.message === "Stop Iteration") return;
}</code>3. The "Fun" Way: Using every()
every() is a better option. It continues iterating through the collection until the callback function returns false. This effectively acts as a break statement.
<code class="javascript">comment.comments.every(function (elem) {
recurs(elem);
if (...) return false;
return true;
});</code>You can also use some() instead of every() if you prefer to return true to break.
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