限制输入只接受括号，不接受字母或数字
[英]Limit input to only accept parentheses, not letters or numbers
问题描述
It should only accept parentheses inside the input.
它应该只接受输入中的括号。 It should not accept letters or numbers它不应该接受字母或数字
function brackets() { var inp = document.getElementById("input").value; var result = document.getElementById("strong").value; console.log(inp,result) var l = 0; var r = 0; for (var i = 0; i < inp.length; i++) { if (inp[i] === "(") { l++; } else if (inp[i] === ")") { r++; } } console.log(l,r) if (l == r) { document.getElementById("strong").innerHTML = "Matched"; } else if (l !== r) { document.getElementById("strong").innerHTML = "Not matched"; } } document.getElementById("input").addEventListener("input",brackets);
<input type="text" id="input" /> <span id="strong"></span>
5 个解决方案
解决方案1
1 2020-09-29 06:31:52
Explanation : I have used keydown event handler.说明：我使用了keydown事件处理程序。 Whenever the key is pressed, it checks if it's a paranthesis or not.每当按键被按下时，它会检查它是否是一个括号。 I case it's not, the input does not gets entered inside the input element.我的情况不是，输入不会被输入到input元素中。
Doing this will avoid input of character, checking if it's not a parenthesis, and removing it if it's not:这样做将避免输入字符，检查它是否不是括号，如果不是，则将其删除：
document.getElementById("input").addEventListener("keydown", function(event) { if (!(event.shiftKey && (event.key == ")" || event.key == "("))) { event.preventDefault(); } });
<input type="text" id="input" />
解决方案2
0 2020-09-29 06:20:18
What you can do is add onchange event listener to the input.您可以做的是将 onchange 事件侦听器添加到输入中。 Then when a user types on the input, you can validate the input to be either "(" or ")" otherwise you clear the input box然后当用户在输入上键入时，您可以验证输入为“(”或“)”，否则清除输入框
解决方案3
0 已采纳 2020-09-29 06:30:24
Do it by checking if the character typed is a parenthesis, and if not, slice the last character.通过检查输入的字符是否是括号来完成，如果不是，则对最后一个字符进行切片。
function brackets() { var inp = document.getElementById("input"); if (inp.value.slice(-1) != '(' && inp.value.slice(-1) != ')') { inp.value = inp.value.slice(0, -1); } }
<input type="text" oninput="brackets()" id="input"/>
解决方案4
0 2020-09-29 06:38:11
Try this:尝试这个：
let inp = document.getElementById('input'); var result = ""; inp.addEventListener('keyup', (e) => { if(inp.value[inp.value.length - 1] === '(' || inp.value[inp.value.length - 1] === ')'){ result += inp.value[inp.value.length - 1] } console.log(result) return result })
<input id="input">
解决方案5
0 2020-09-29 06:49:24
First, I suggest using regexp and the pattern attribute.首先，我建议使用正则表达式和模式属性。 https://www.w3schools.com/tags/att_input_pattern.asp https://www.w3schools.com/tags/att_input_pattern.asp
input:invalid { border: red solid 3px; }
<!DOCTYPE html> <html> <head> </head> <body> <p>An input that CANNOT contain parenthesis</p> <input type="search" id="search" name="search" pattern="[^()]+" title="Invalid input"> </body> </html>
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