javascript - 从文本框中复制前两个值

Question

如何仅使用此代码复制前两个字母？我真的不知道怎么办

function sync() {
    var c = document.getElementById('c');
    var a = document.getElementById('a');
    a.value = c.value;
}

Answer 1

您可以使用字符串切片方法:

MyString.slice(0,2); //returns a new string with only the first two chars.

所以你可以写:

function sync() {
    var c = document.getElementById('c');
    var a = document.getElementById('a');
    a.value = c.value.slice(0,2);// a now contains the first two chars from c
}