輸入的占位符不會從<select>
[英]Input's placeholder won't change from <select>
問題描述
因此，基本上我想要實現的是在更改選擇內容時更改輸入的占位符。 第一個輸入成功更改，但似乎與第二個輸入不同。 下面是我正在使用的代碼：
function onChange(fromOrTo) { if (fromOrTo = 'from') { document.getElementById("from").placeholder = document.getElementById("selectFrom").value; } else if (fromOrTo = 'to') { document.getElementById("to").placeholder = document.getElementById("selectTo").value; } }
<body> <div id="sect"> <section> <select onchange="onChange('from')" id="selectFrom"> <option value="Celcius">Celcius</option> <option value="Farenheit">Farenheit</option> <option value="Kelvin">Kelvin</option> <option value="Reamur">Reamur</option> </select> <span class="toText">to</span> <select onchange="onChange('to')" id="selectTo"> <option value="Celcius">Celcius</option> <option value="Farenheit">Farenheit</option> <option value="Kelvin">Kelvin</option> <option value="Reamur">Reamur</option> </select> </section> <section> <input type="text" id="from"> <span id="toText">to</span> <input type="text" id="to"> </section> </div> </body>
2 個解決方案
解決方案1
1 2018-03-02 02:22:35
您只需要與===而不是=進行比較
function onChange(fromOrTo) { if (fromOrTo === 'from') { document.getElementById("from").placeholder = document.getElementById("selectFrom").value; } else if (fromOrTo === 'to') { document.getElementById("to").placeholder = document.getElementById("selectTo").value; } }
<body> <div id="sect"> <section> <select onchange="onChange('from')" id="selectFrom"> <option value="Celcius">Celcius</option> <option value="Farenheit">Farenheit</option> <option value="Kelvin">Kelvin</option> <option value="Reamur">Reamur</option> </select> <span class="toText">to</span> <select onchange="onChange('to')" id="selectTo"> <option value="Celcius">Celcius</option> <option value="Farenheit">Farenheit</option> <option value="Kelvin">Kelvin</option> <option value="Reamur">Reamur</option> </select> </section> <section> <input type="text" id="from"> <span id="toText">to</span> <input type="text" id="to"> </section> </div> </body>
解決方案2
0 2018-03-02 02:23:36
你只需要在你的每一個等號if條件句。 這將分配給變量，而不是對其進行比較 。 切換到兩個等號（或三個以避免類型強制）將解決此問題：
function onChange(fromOrTo) { if (fromOrTo === 'from') { document.getElementById("from").placeholder = document.getElementById("selectFrom").value; } else if (fromOrTo === 'to') { document.getElementById("to").placeholder = document.getElementById("selectTo").value; } }
<body> <div id="sect"> <section> <select onchange="onChange('from')" id="selectFrom"> <option value="Celcius">Celcius</option> <option value="Farenheit">Farenheit</option> <option value="Kelvin">Kelvin</option> <option value="Reamur">Reamur</option> </select> <span class="toText">to</span> <select onchange="onChange('to')" id="selectTo"> <option value="Celcius">Celcius</option> <option value="Farenheit">Farenheit</option> <option value="Kelvin">Kelvin</option> <option value="Reamur">Reamur</option> </select> </section> <section> <input type="text" id="from"> <span id="toText">to</span> <input type="text" id="to"> </section> </div> </body>
React select 自定義輸入不會隱藏占位符
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