如何在Javascript中打印出行 [英] How to print out line in Javascript

问题描述

我想测试此函数的返回值getFileExtension(input.files [0] .name)(我在此处指出要指向该行的注释)我的问题是如何在javascript中打印出该值?谢谢！

I want to test the return value of this function getFileExtension(input.files[0].name) (I have a comment there to point at that line) My question is how to print out that value in javascript? Thanks!

<script>
    function getFileExtension(filename) {
        var ext=filename.split('.').pop();
        return ext
    }
</script>

<input type='file' onchange="readURL(this);"> 

<script>
function readURL(input) {
    if (input.files && input.files[0]) {
        if (getFileExtension(input.files[0].name)=="png") { // this line is our problem 
            var reader = new FileReader();
            reader.onload = function (e) {
                document.getElementById("pdf").innerHTML="<img id='blah' src=" +
                                       e.target.result + " alt='your image' width='450'>"
            }
            reader.readAsDataURL(input.files[0]);
        }
    }
}
</script>

推荐答案

您可以通过编写

console.log(value);

大多数浏览器都有一个控制台，您可以通过按 f12 来查看.值将在那里结束.

Most browsers have a console which you can see by pressing f12. The values will end up there.

如果您使用的是Internet Explorer，请记住要打开开发人员工具(f12)，否则会出现错误.

If you are using Internet explorer remember to have developer tools open (f12) or you will get an error.

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