如何在 Typescript 中使用 break 语句

Question

I'm new to Javascript. I started with a very basic project in Angular ie Form validation. In my case I've to call my custom method, validationTest() within itself only once. If I do not put any break condition then there will be too many recursions. I have to stop this. I tried many other solutions:

1. Break Statement in TypeScript
2. TypeScript - Loops

I followed them very carefully, but I'm getting this:

Module parse failed: Unsyntactic break (84:12)

Here's my code:

validationTest() {
    let count =0;
    this.isAnyRangeInvalid = false;
    this.monthpicker.forEach(picker => {
        if (picker.isValidRange === false) {
            this.isAnyRangeInvalid = true;
        }
    });
    count ++;
    if(count===1) {
        break;
    }
    this.validationTest();
}

Even VScode editor is also showing a red zig-zag line under the token break . I'm coming from Java and CPP background. Please correct me.

Answer 1

To stop a function from executing, use return . break only makes sense in the context of a for or while loop.

But another problem is that your validationTest doesn't have a persistent view of the count variable - it's completely local, so the test isn't going to work anyway. Consider passing a parameter instead, which will indicate whether the current call is recursive or not:

validationTest(lastTry = false) {
    this.isAnyRangeInvalid = false;
    this.monthpicker.forEach(picker => {
        if (picker.isValidRange === false) {
            this.isAnyRangeInvalid = true;
        }
    });
    if (!lastTry) this.validationTest(true);
}

Make sure that the initial call of validationTest doesn't pass a parameter, or passes false .

For a more general solution of limiting yourself to N recursive tries, you can pass around a number instead, eg:

validationTest(triesLeft = 3) {
    this.isAnyRangeInvalid = false;
    this.monthpicker.forEach(picker => {
        if (picker.isValidRange === false) {
            this.isAnyRangeInvalid = true;
        }
    });
    if (triesLeft !== 0) this.validationTest(triesLeft - 1);
}