When it comes to break, we all know that break is often used in writing loops. Here is a summary of some knowledge about break.

1. Traverse a large amount of data remember to use break to jump out of the loop

What do you mean? Simply put, when I have a thousand different disordered data arrays, I need to traverse them, but this data may be the first element or the last element.
Compare the following two pieces of code:
code 1:

var result;
for(var i = 0; i < 1000; i++) {
    //arr and value "need" are already known
    if(arr[i] == value_need) {
        result = arr[i]; 
    }
}

code 2:

var result;
for(var i = 0; i < 1000; i++) {
    //arr and value "need" are already known
    if(arr[i] == value_need) {
        result = arr[i];
        break; 
    }
}

The second one is better.

2. break just jumps out of a loop

Don't get this wrong.

var sum = 0;

for(var i = 0; i < 10; i++) {
    for(var j = 0; j < 10; j++) {
        if(j == 5) break;
        sum++;
    }
}

console.log('sum: ' + sum);    //sum: 50

Do you see that i increases from 0 to 9, and j increases 5 times from 0 to 4 each time. A total of 50. If it can jump out of multiple loops, sum should be 5.

Now that I've said break, I'd like to say continue by the way.
code 1:

var sum = 0;

for(var i = 0; i < 10; i++) {
    if(i == 5) continue;
    sum++;
}

console.log('sum: ' + sum);    //sum: 9

code 2:

var sum = 0;

for(var i = 0; i < 10; i++) {
    for(var j = 0; j < 10; j++) {
        if(i == 5 && j == 5) continue;
        sum++;
    }
}

console.log('sum: ' + sum);    //sum: 99

See, that is to skip this cycle.

3. Jump out of multiple loops

break and tag statements are needed to work. The syntax of a label statement is this: Label: statement.

var sum = 0;

outState:
for(var i = 0; i < 10; i++) {
    for(var j = 0; j < 10; j++) {
        if(j == 5) break outState;
        sum++;
    }
}

console.log('sum: ' + sum);    //sum: 5

See? If i execute it five times when i is 0, i will jump out of the whole double cycle.
Take a look at continue's:

var sum = 0;

outState:
for(var i = 0; i < 10; i++) {
    for(var j = 0; j < 10; j++) {
        if(j == 5) continue outState;
        sum++;
    }
}

console.log('sum: ' + sum);    //sum: 50

Every time j to 5, i don't do it. Go to the outer i loop. i go from 0 to 9, five times at a time, that's 50.