setInteral()方法允许我们在每个特定时间段后连续触发回调函数。我们可以将回调函数作为第一个参数传递给每个时间段后触发,并将以毫秒为单位的时间段作为第二个参数。
setInterval() 方法在第一次特定的毫秒数后调用回调函数。现在的问题是,我们需要在第一次0毫秒立即调用回调函数,之后,我们需要在给定的时间段内连续调用它。
示例
在下面的示例中,我们创建了 func() 函数,该函数打印文档中的消息。我们使用了 setInterval() 方法,该方法每 3000 毫秒调用一次 func() 函数。
<html> <body> <h3 id="Using-the-i-setInteral-i-method-to-invoke-the-particular-function-continuosly"> Using the <i> setInteral() </i> method to invoke the particular function continuosly </h3> <div id = "output"> </div> <script> let output = document.getElementById('output'); output.innerHTML += "Please wait ...." + "<br>"; function func() { output.innerHTML += "The func() function is invoked!" + "<br>"; } setInterval(func, 3000); </script> </body> </html>
在输出中,用户可以观察到 setInteraval() 方法在 3000 毫秒后首次调用 func() 函数。
用户可以按照以下方式在0毫秒处首次调用func()函数。
第一次调用该函数,之后使用setInterval()方法
使用 setInterval() 方法时,首次无延迟调用该函数的一种方法是首次调用该函数。
当我们第一次调用该函数时,它会在第 0 毫秒执行。之后,setInterval()方法会在一定时间后连续执行该函数。
语法
用户第一次使用setInterval()方法时,可以按照下面的语法立即调用该函数。
func_name() setInterval(func_name, 1000);
在上面的语法中,我们第一次调用了 func_name() 函数,之后每 1000 毫秒调用一次。
示例
在下面的示例中,func() 函数使用 setInterval() 方法每 1000 毫秒调用一次消息。为了不延迟地第一次调用该函数,我们首先调用该函数,然后使用 setInteral() 方法调用该函数。
<html> <body> <h3 id="Invoking-the-function-for-the-first-time-and-after-that-using-the-setInteral-method-to-invoke-the-particular-function-continuously"> Invoking the function for the first time and, after that, using the setInteral() method to invoke the particular function continuously. </h3> <div id = "output"> </div> </body> <script> let output = document.getElementById('output'); function func() { output.innerHTML += "The func() function is invoked!" + "<br>"; } func() setInterval(func, 1000); </script> </html>
在setInteral()方法中创建立即调用的函数
一旦我们创建函数表达式,立即调用的函数就会立即调用它。因此,我们可以使用立即调用函数表达式来首次调用该函数,而无需延迟。我们还可以在函数内部使用setInterval()方法来以特定的时间间隔执行函数。
语法
用户在使用 setInterval() 方法时,可以按照以下语法使用立即调用的函数表达式来无延迟地执行函数。
(function name() { setInterval(name, 3000); })()
在上面的语法中,我们在大括号中编写了函数表达式,然后编写左大括号和右大括号以立即调用该函数。
示例 3
下面的示例创建一个测试函数,使用 setInterval() 方法在每个时间间隔后调用。我们将 test() 函数编写为立即调用的函数表达式,并在函数内使用 setInterval() 方法,每 3000 毫秒调用一次 test() 函数。
我们可以观察到测试函数在刷新网页时第一次在第 0 毫秒调用的输出,然后每 3000 毫秒调用一次。
<html> <body> <h3 id="Using-the-immediately-invoked-function-expression-to-invoke-the-function-without-delay-for-the-first-time-while-using-the-setInteral-method"> Using the immediately invoked function expression to invoke the function without delay for the first time while using the setInteral() method </h3> <div id = "output"> </div> <script> let output = document.getElementById('output'); (function test() { output.innerHTML += "The test() function is invoked!" + "<br>"; setInterval(test, 3000); })() </script> </body> </html>
用户第一次学会了如何无延迟地调用 setInterval() 方法中使用的函数。用户可以第一次调用该函数,也可以使用立即调用的函数表达式。
建议首次调用该函数,而不是使用立即调用的函数表达式,因为它会递归调用该函数。经过一段时间间隔后,当我们在其中使用 setInterval() 方法时,立即调用的函数表达式会无限次调用该函数。
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