如何检查我的输入中是否有文字

Question

我想做一个小程序，将检查我在输入字段中是否有任何文本...如果它是一个数字，我就很容易做

cardsp.value >= 1    

但是，当输入为文本时，如何检查字段中是否有内容？

Name : <input id="namep" type="text" />

我试图做类似的事情（js），但这可能是某人做过的最错误的方式

    var array= ["","a","b","c","d","e","f","g","h","i","j","k","m","n","l","o","p","q","r","s","t","u","v","w","x","y","z"];
function pay()  {
    namep.value 
    if(namep.value >= array.indexOf("a"), cardsp.value >= 1 , emailpa.value >= 1){

         alert('Ty For Buying a Ticket From our compeny , you will receive the Invoicing in the ' +emailpa.value);
        }

    else if(namep.value == array.indexOf(""){
            alert('Please Write Your Name');
    }

    }

Answer 1

您可以通过以下方式检查输入字段是否仅包含字母：

var letters = /^[a-z]+$/;  
if( namep.value.match(letters) ) {
  // string contains only letters.
}

Answer 2

 var input=$("#namep").val();

要么

var input = document.getElementById('namep').value;

然后检查是否有东西...

if(input.length>0)
{
 //do something. 
}

要么

var inputLength = input.length;

if(inputLength>0)
{
 //do something. 
}