https://developers.google.com/web/tools/chrome-devtools/javascript/step-code
step over next function call
Executes whatever happens on the next line and jumps to the next line.
step into next function call
If the next line contains a function call, Step Into will jump to and pause that function at its first line.
step out of current function
Executes the remainder剩余部分 of the current function and then pauses at the next statement after the function call.