How to set a breakpoint at a lambda call in Google

问题:

I use Babel and Google Chrome Developer Tools with JavaScript source maps enabled. Given this code

function myFunc(elements) {
  return elements
    .map(element => element.value)
    .filter(value => value >= 0);
}

how can I pause execution at execution of lambda function element => element.value? If I set a breakpoint at line of .map(element => element.value) it will only pause when map is executed, but not when the lambda function is executed.

回答1:

This feature is finally available (at least in Google Chrome 58). Click on the line number of the line of your lambda you like to debug (here line 3). Then activate the marker in your lambda (here the second) by clicking it. Further, I disabled the first marker here, which would pause on the map call (not the lambda):

When your program runs and hits the breakpoint, it will pause and you can inspect variables:

回答2:

You can use the debugger keyword to signal the debugger to pause at that location and it can be inserted just like any JavaScript statement.

function myFunc(elements) {
  return elements
    .map(element => {debugger; return element.value})
    .filter(value => value >= 0);
}

回答3:

You can do as follows:

    function myFunc(elements) {
      return elements
        .map(element => {
           element.value
        })
        .filter(value => value >= 0);
    }

This way you can add a breakpoint in line element.value

Couldn't find a way to get it work without code changing.
If anybody can find a way please tell.