简单计时器-为什么使用setTimeout（）的函数内部的函数调用失败？

Question

I am learning some JavaScript and experimenting with a simple countdown timer. The countdown fails if I insert checkTime() in the timedCount() function. I want the script to display a message in the 'warning' div, when the seconds remaining (var c) is a given integer (in this case 100 sec). When I insert the checkTime() function the script displays 100 and stops. It does the same when I put the function inside timeCount() function. I'm stumped!

 var c = 120; var t; var timer_is_on = 0; start.onclick = startCount; reset.onclick = resetCount; function timedCount() { document.getElementById("clock").innerHTML = c; c = c - 1; checkTime(); t = setTimeout(function() { timedCount() }, 1000); } function startCount() { if (!timer_is_on) { timer_is_on = 1; timedCount(); document.getElementById('start').style.display = 'none'; document.getElementById('reset').style.display = 'none'; document.getElementById('stop').style.display = 'block'; } } function stopCount() { clearTimeout(t); timer_is_on = 0; document.getElementById('start').style.display = 'block'; document.getElementById("start").innerHTML = "Resume"; document.getElementById('reset').style.display = 'block'; document.getElementById('stop').style.display = 'none'; } function resetCount() { clearTimeout(t); c = 0; timer_is_on = 0; document.getElementById("txt").value = 0; document.getElementById('start').style.display = 'block'; document.getElementById("start").innerHTML = "Start!"; } function checkTime() { if (c = 100) { document.getElementById("warning").innerHTML = "Time nearly up!"; } } 

 <div style="font-size:30px;"><span id="clock">0</span> <span>:seconds</span></div> <div id="warning"></div> <button id="start">Start count!</button> <button id="stop" onclick="stopCount()">Pause!</button> <button id="reset">Reset!</button> 

Answer 1

（c = 100）应该是（c === 100），您打算在要检查是否相等时设置。