使用javascript使用选择（组合框）输入更改段落文本

Question

I'm trying to change all instances the word "blue" in a paragraph to another colour based on combo box input; the colour of the word changes to the corresponding input. Not sure what else to try. You can check my attached code.

 document.querySelector(document).ready(function() { var button = document.querySelector("button_change"); document.querySelector(button).click(function() { var select = document.querySelector("input_color").value; var element = document.querySelector(".cow_color"); document.querySelector(element).html(inputValue); }); });

 <h2> <span class="cow_color">Blue</span> Cow by Gelett Burgess (published in The Lark, 1895) </h2> <p> I never saw a <span class="cow_color">Blue</span> Cow, I never hope to see one; But I can tell you, anyhow, I'd rather see than be one. </p> <p> Change the cow's color to: <select id="input_color"> <option value="Purple">Purple</option> <option value="Green">Green</option> <option value="Red">Red</option> <option value="Yellow">Yellow</option> <option value="Teal">Teal</option> </select> <button id="button_change">Change!</button> </p>

Answer 1

1. You either need an eventListener or an onclick-trigger to run the script.
2. you use element.querySelectorAll('.class-name') as selector to select all classes with that class name
3. to apply the changes to all elements you use the .forEach(el => el.command) command.

final JS line should be:

document.querySelectorAll('.cow_color').forEach(el => elinnerHTML = document.querySelectorAll('#input_color').value;);

 function changeColor() { var inputValue = document.querySelector('#input_color'), cowColor = document.querySelectorAll('.cow_color'); cowColor.forEach(el => el.innerHTML = inputValue.value); }

 <h2> <span class="cow_color">Blue</span> Cow by Gelett Burgess (published in The Lark, 1895) </h2> <p> I never saw a <span class="cow_color">Blue</span> Cow, I never hope to see one; But I can tell you, anyhow, I'd rather see than be one. </p> <p> Change the cow's color to: <select id="input_color"> <option value="Purple">Purple</option> <option value="Green">Green</option> <option value="Red">Red</option> <option value="Yellow">Yellow</option> <option value="Teal">Teal</option> </select> <button id="button_change" onclick="changeColor()">Change!</button> </p>

Answer 2

Overview

Heres a jquery version

Example

Example

Explination:

we bind to the button, then on click event, we get the value from the dropdown selection. with that value we loop through all .cow_color and assign the color with the value we got previously and also it replaces the Text.

Code

 $(document).on('click', '#button_change', (element) => { let color = $('#input_color').val(); let spans = $('.cow_color'); spans.map(function() { $(this).css('color', color); $(this).html(color); }); return; });

 <!-- Jquery --> <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.5.1/jquery.min.js"></script> <!-- Body --> <h2> <span class="cow_color">Blue</span> Cow by Gelett Burgess (published in The Lark, 1895) </h2> <p> I never saw a <span class="cow_color">Blue</span> Cow, I never hope to see one; But I can tell you, anyhow, I'd rather see than be one. </p> <p> Change the cow's color to: <select id="input_color"> <option value="Purple">Purple</option> <option value="Green">Green</option> <option value="Red">Red</option> <option value="Yellow">Yellow</option> <option value="Teal">Teal</option> </select> <button id="button_change">Change!</button> </p>