[josh-haywood]

Im trying to make a theme toggle button for my web page. I’m starting just trying to make the SVGs toggle based on whether your currently on dark mode or light mode. I have tested and the buttons work fine when transferring from one to the other. However when I then try and toggle back it doesnt work, could someone offer a solution please.

function ToggleTheme() {
    var themeToggleDark = document.getElementsByClassName("theme-toggle-dark")[0];
    var themeToggleLight = document.getElementsByClassName("theme-toggle-light")[0];

    if (themeToggleLight.style.visibility = "hidden") {
        themeToggleDark.style.visibility = "visible";
    }

    else {
        themeToggleDark.style.visibility = "hidden";
    }
}

<svg width="100px" class="theme-toggle-dark" alt="Icon used for changing site theme to dark" onclick="ToggleTheme()" aria-hidden="true" focusable="false" data-prefix="far" data-icon="moon" class="svg-inline--fa fa-moon fa-w-16" role="img" xmlns="http://www.w3.org/2000/svg" viewBox="0 0 512 512"><path fill="currentColor" d="M279.135 512c78.756 0 150.982-35.804 198.844-94.775 28.27-34.831-2.558-85.722-46.249-77.401-82.348 15.683-158.272-47.268-158.272-130.792 0-48.424 26.06-92.292 67.434-115.836 38.745-22.05 28.999-80.788-15.022-88.919A257.936 257.936 0 0 0 279.135 0c-141.36 0-256 114.575-256 256 0 141.36 114.576 256 256 256zm0-464c12.985 0 25.689 1.201 38.016 3.478-54.76 31.163-91.693 90.042-91.693 157.554 0 113.848 103.641 199.2 215.252 177.944C402.574 433.964 344.366 464 279.135 464c-114.875 0-208-93.125-208-208s93.125-208 208-208z"></path></svg>
<svg width="100px" class="theme-toggle-light" alt="Icon used for changing site theme to light" onclick="ToggleTheme()" aria-hidden="true" focusable="false" data-prefix="far" data-icon="sun" class="svg-inline--fa fa-sun fa-w-16" role="img" xmlns="http://www.w3.org/2000/svg" viewBox="0 0 512 512"><path fill="currentColor" d="M494.2 221.9l-59.8-40.5 13.7-71c2.6-13.2-1.6-26.8-11.1-36.4-9.6-9.5-23.2-13.7-36.2-11.1l-70.9 13.7-40.4-59.9c-15.1-22.3-51.9-22.3-67 0l-40.4 59.9-70.8-13.7C98 60.4 84.5 64.5 75 74.1c-9.5 9.6-13.7 23.1-11.1 36.3l13.7 71-59.8 40.5C6.6 229.5 0 242 0 255.5s6.7 26 17.8 33.5l59.8 40.5-13.7 71c-2.6 13.2 1.6 26.8 11.1 36.3 9.5 9.5 22.9 13.7 36.3 11.1l70.8-13.7 40.4 59.9C230 505.3 242.6 512 256 512s26-6.7 33.5-17.8l40.4-59.9 70.9 13.7c13.4 2.7 26.8-1.6 36.3-11.1 9.5-9.5 13.6-23.1 11.1-36.3l-13.7-71 59.8-40.5c11.1-7.5 17.8-20.1 17.8-33.5-.1-13.6-6.7-26.1-17.9-33.7zm-112.9 85.6l17.6 91.2-91-17.6L256 458l-51.9-77-90.9 17.6 17.6-91.2-76.8-52 76.8-52-17.6-91.2 91 17.6L256 53l51.9 76.9 91-17.6-17.6 91.1 76.8 52-76.8 52.1zM256 152c-57.3 0-104 46.7-104 104s46.7 104 104 104 104-46.7 104-104-46.7-104-104-104zm0 160c-30.9 0-56-25.1-56-56s25.1-56 56-56 56 25.1 56 56-25.1 56-56 56z"></path></svg>

Images

Before onClick

After onClick

Im trying to get from the moon icon back to the sun icon after ive clicked im summary.

[james]

You don’t seem to have code that changes themeToggleLight.style.visibility. Does this help?

if (themeToggleLight.style.visibility == "hidden") {
    themeToggleLight.style.visibility = "visible";
    themeToggleDark.style.visibility = "hidden";
} else {
    themeToggleLight.style.visibility = "hidden";
    themeToggleDark.style.visibility = "visible";
}

[ikhvjs]

Add a class hide-button to hide the svg together with the toggle funciton.

function ToggleTheme() {
    const svgs = document.querySelectorAll("svg");
    svgs.forEach(btn => {
        btn.classList.toggle("hide-button");
    });
}

.hide-button {
  display:none;
}

<svg width="100px" class="theme-toggle-dark" alt="Icon used for changing site theme to dark" onclick="ToggleTheme()" aria-hidden="true" focusable="false" data-prefix="far" data-icon="moon" class="svg-inline--fa fa-moon fa-w-16" role="img" xmlns="http://www.w3.org/2000/svg" viewBox="0 0 512 512"><path fill="currentColor" d="M279.135 512c78.756 0 150.982-35.804 198.844-94.775 28.27-34.831-2.558-85.722-46.249-77.401-82.348 15.683-158.272-47.268-158.272-130.792 0-48.424 26.06-92.292 67.434-115.836 38.745-22.05 28.999-80.788-15.022-88.919A257.936 257.936 0 0 0 279.135 0c-141.36 0-256 114.575-256 256 0 141.36 114.576 256 256 256zm0-464c12.985 0 25.689 1.201 38.016 3.478-54.76 31.163-91.693 90.042-91.693 157.554 0 113.848 103.641 199.2 215.252 177.944C402.574 433.964 344.366 464 279.135 464c-114.875 0-208-93.125-208-208s93.125-208 208-208z"></path></svg>
<svg width="100px" class="theme-toggle-light hide-button" alt="Icon used for changing site theme to light" onclick="ToggleTheme()" aria-hidden="true" focusable="false" data-prefix="far" data-icon="sun" class="svg-inline--fa fa-sun fa-w-16" role="img" xmlns="http://www.w3.org/2000/svg" viewBox="0 0 512 512"><path fill="currentColor" d="M494.2 221.9l-59.8-40.5 13.7-71c2.6-13.2-1.6-26.8-11.1-36.4-9.6-9.5-23.2-13.7-36.2-11.1l-70.9 13.7-40.4-59.9c-15.1-22.3-51.9-22.3-67 0l-40.4 59.9-70.8-13.7C98 60.4 84.5 64.5 75 74.1c-9.5 9.6-13.7 23.1-11.1 36.3l13.7 71-59.8 40.5C6.6 229.5 0 242 0 255.5s6.7 26 17.8 33.5l59.8 40.5-13.7 71c-2.6 13.2 1.6 26.8 11.1 36.3 9.5 9.5 22.9 13.7 36.3 11.1l70.8-13.7 40.4 59.9C230 505.3 242.6 512 256 512s26-6.7 33.5-17.8l40.4-59.9 70.9 13.7c13.4 2.7 26.8-1.6 36.3-11.1 9.5-9.5 13.6-23.1 11.1-36.3l-13.7-71 59.8-40.5c11.1-7.5 17.8-20.1 17.8-33.5-.1-13.6-6.7-26.1-17.9-33.7zm-112.9 85.6l17.6 91.2-91-17.6L256 458l-51.9-77-90.9 17.6 17.6-91.2-76.8-52 76.8-52-17.6-91.2 91 17.6L256 53l51.9 76.9 91-17.6-17.6 91.1 76.8 52-76.8 52.1zM256 152c-57.3 0-104 46.7-104 104s46.7 104 104 104 104-46.7 104-104-46.7-104-104-104zm0 160c-30.9 0-56-25.1-56-56s25.1-56 56-56 56 25.1 56 56-25.1 56-56 56z"></path></svg>

[phucbm]

= is not a safe comparison operator, you should use === or !==. At first, when visibility is not set, your result would be an empty string so it’s better to compare with hidden as a value.

if (themeToggleLight.style.visibility !== "hidden") {
    themeToggleLight.style.visibility = "hidden";
    themeToggleDark.style.visibility = "visible";
} else {
    themeToggleLight.style.visibility = "visible";
    themeToggleDark.style.visibility = "hidden";
}

I also edit the visibility to display for a better effect.

function ToggleTheme() {
  var themeToggleDark = document.querySelector(".theme-toggle-dark");
  var themeToggleLight = document.querySelector(".theme-toggle-light");

  if (themeToggleLight.style.display !== "none") {
    themeToggleLight.style.display = "none";
    themeToggleDark.style.display = "block";
  } else {
    themeToggleLight.style.display = "block";
    themeToggleDark.style.display = "none";
  }
}
ToggleTheme()

svg {
  width: 50px;
}

<svg class="theme-toggle-dark" alt="Icon used for changing site theme to dark" onclick="ToggleTheme()" aria-hidden="true" focusable="false" data-prefix="far" data-icon="moon" class="svg-inline--fa fa-moon fa-w-16" role="img" xmlns="http://www.w3.org/2000/svg"
  viewBox="0 0 512 512"><path fill="currentColor" d="M279.135 512c78.756 0 150.982-35.804 198.844-94.775 28.27-34.831-2.558-85.722-46.249-77.401-82.348 15.683-158.272-47.268-158.272-130.792 0-48.424 26.06-92.292 67.434-115.836 38.745-22.05 28.999-80.788-15.022-88.919A257.936 257.936 0 0 0 279.135 0c-141.36 0-256 114.575-256 256 0 141.36 114.576 256 256 256zm0-464c12.985 0 25.689 1.201 38.016 3.478-54.76 31.163-91.693 90.042-91.693 157.554 0 113.848 103.641 199.2 215.252 177.944C402.574 433.964 344.366 464 279.135 464c-114.875 0-208-93.125-208-208s93.125-208 208-208z"></path></svg>
<svg class="theme-toggle-light active" alt="Icon used for changing site theme to light" onclick="ToggleTheme()" aria-hidden="true" focusable="false" data-prefix="far" data-icon="sun" class="svg-inline--fa fa-sun fa-w-16" role="img" xmlns="http://www.w3.org/2000/svg"
  viewBox="0 0 512 512"><path fill="currentColor" d="M494.2 221.9l-59.8-40.5 13.7-71c2.6-13.2-1.6-26.8-11.1-36.4-9.6-9.5-23.2-13.7-36.2-11.1l-70.9 13.7-40.4-59.9c-15.1-22.3-51.9-22.3-67 0l-40.4 59.9-70.8-13.7C98 60.4 84.5 64.5 75 74.1c-9.5 9.6-13.7 23.1-11.1 36.3l13.7 71-59.8 40.5C6.6 229.5 0 242 0 255.5s6.7 26 17.8 33.5l59.8 40.5-13.7 71c-2.6 13.2 1.6 26.8 11.1 36.3 9.5 9.5 22.9 13.7 36.3 11.1l70.8-13.7 40.4 59.9C230 505.3 242.6 512 256 512s26-6.7 33.5-17.8l40.4-59.9 70.9 13.7c13.4 2.7 26.8-1.6 36.3-11.1 9.5-9.5 13.6-23.1 11.1-36.3l-13.7-71 59.8-40.5c11.1-7.5 17.8-20.1 17.8-33.5-.1-13.6-6.7-26.1-17.9-33.7zm-112.9 85.6l17.6 91.2-91-17.6L256 458l-51.9-77-90.9 17.6 17.6-91.2-76.8-52 76.8-52-17.6-91.2 91 17.6L256 53l51.9 76.9 91-17.6-17.6 91.1 76.8 52-76.8 52.1zM256 152c-57.3 0-104 46.7-104 104s46.7 104 104 104 104-46.7 104-104-46.7-104-104-104zm0 160c-30.9 0-56-25.1-56-56s25.1-56 56-56 56 25.1 56 56-25.1 56-56 56z"></path></svg>

[3rdthemagical]

Just swap visibility values.

function toggleTheme() {
  const darkThemeBtn = document.getElementsByClassName("theme-toggle-dark")[0];
  const lightThemeBtn = document.getElementsByClassName("theme-toggle-light")[0];

  const darkThemeState = darkThemeBtn.style.visibility;

  darkThemeBtn.style.visibility = lightThemeBtn.style.visibility;
  lightThemeBtn.style.visibility = darkThemeState;
}

[satch]

You missed another equal sign to create the comparator == on the conditional, resulting to the visibility being always hidden for the themeToggleLight object. Furthermore, you need to make the themeToggleDark visible if you’re testing for themeToggleLight to be hidden.

Here’s the fixed code:

function ToggleTheme() {
    var themeToggleDark = document.getElementsByClassName("theme-toggle-dark")[0];
    var themeToggleLight = document.getElementsByClassName("theme-toggle-light")[0];

    if (themeToggleLight.style.visibility == "hidden") {
        themeToggleDark.style.visibility = "hidden";
        themeToggleLight.style.visibility = "visible";
    }

    else {
        themeToggleDark.style.visibility = "visible";
        themeToggleLight.style.visibility = "hidden";
    }
}

<div style="max-width:50px;">
  <svg class="theme-toggle-dark" alt="Icon used for changing site theme to dark" onclick="ToggleTheme()" aria-hidden="true" focusable="false" data-prefix="far" data-icon="moon" class="svg-inline--fa fa-moon fa-w-16" role="img" xmlns="http://www.w3.org/2000/svg" viewBox="0 0 512 512"><path fill="currentColor" d="M279.135 512c78.756 0 150.982-35.804 198.844-94.775 28.27-34.831-2.558-85.722-46.249-77.401-82.348 15.683-158.272-47.268-158.272-130.792 0-48.424 26.06-92.292 67.434-115.836 38.745-22.05 28.999-80.788-15.022-88.919A257.936 257.936 0 0 0 279.135 0c-141.36 0-256 114.575-256 256 0 141.36 114.576 256 256 256zm0-464c12.985 0 25.689 1.201 38.016 3.478-54.76 31.163-91.693 90.042-91.693 157.554 0 113.848 103.641 199.2 215.252 177.944C402.574 433.964 344.366 464 279.135 464c-114.875 0-208-93.125-208-208s93.125-208 208-208z"></path></svg>
  <svg class="theme-toggle-light" alt="Icon used for changing site theme to light" onclick="ToggleTheme()" aria-hidden="true" focusable="false" data-prefix="far" data-icon="sun" class="svg-inline--fa fa-sun fa-w-16" role="img" xmlns="http://www.w3.org/2000/svg" viewBox="0 0 512 512"><path fill="currentColor" d="M494.2 221.9l-59.8-40.5 13.7-71c2.6-13.2-1.6-26.8-11.1-36.4-9.6-9.5-23.2-13.7-36.2-11.1l-70.9 13.7-40.4-59.9c-15.1-22.3-51.9-22.3-67 0l-40.4 59.9-70.8-13.7C98 60.4 84.5 64.5 75 74.1c-9.5 9.6-13.7 23.1-11.1 36.3l13.7 71-59.8 40.5C6.6 229.5 0 242 0 255.5s6.7 26 17.8 33.5l59.8 40.5-13.7 71c-2.6 13.2 1.6 26.8 11.1 36.3 9.5 9.5 22.9 13.7 36.3 11.1l70.8-13.7 40.4 59.9C230 505.3 242.6 512 256 512s26-6.7 33.5-17.8l40.4-59.9 70.9 13.7c13.4 2.7 26.8-1.6 36.3-11.1 9.5-9.5 13.6-23.1 11.1-36.3l-13.7-71 59.8-40.5c11.1-7.5 17.8-20.1 17.8-33.5-.1-13.6-6.7-26.1-17.9-33.7zm-112.9 85.6l17.6 91.2-91-17.6L256 458l-51.9-77-90.9 17.6 17.6-91.2-76.8-52 76.8-52-17.6-91.2 91 17.6L256 53l51.9 76.9 91-17.6-17.6 91.1 76.8 52-76.8 52.1zM256 152c-57.3 0-104 46.7-104 104s46.7 104 104 104 104-46.7 104-104-46.7-104-104-104zm0 160c-30.9 0-56-25.1-56-56s25.1-56 56-56 56 25.1 56 56-25.1 56-56 56z"></path></svg>
</div>

[rook218]

There were a couple issues:

1. You were assigning with a single equal sign = instead of checking equality with a double or triple equal sign == or ===

2. You weren’t toggling both buttons, just setting the dark to turn on and off, so your light button was always on and since the condition was whether the light button was on or off, it would never enter the else block.

function ToggleTheme() {
    var themeToggleDark = document.getElementsByClassName("theme-toggle-dark")[0];
    var themeToggleLight = document.getElementsByClassName("theme-toggle-light")[0];
    // if it's currently in dark mode (light mode icon is available), turn it to light mode
    // (turn off light mode icon, turn on dark mode icon)
    if (themeToggleLight.style.visibility == "visible") {
        themeToggleLight.style.visibility = "hidden";
        themeToggleDark.style.visibility = "visible";
    }
    // else turn on dark mode (turn off light mode icon, turn on dark mode icon)
    else {
        themeToggleLight.style.visibility = "visible";
        themeToggleDark.style.visibility = "hidden";
    }
    
}

ToggleTheme();

    <svg width="50px" height="50px" class="theme-toggle-dark" alt="Icon used for changing site theme to dark" onclick="ToggleTheme()" aria-hidden="true" focusable="false" data-prefix="far" data-icon="moon" class="svg-inline--fa fa-moon fa-w-16" role="img" xmlns="http://www.w3.org/2000/svg" viewBox="0 0 512 512"><path fill="currentColor" d="M279.135 512c78.756 0 150.982-35.804 198.844-94.775 28.27-34.831-2.558-85.722-46.249-77.401-82.348 15.683-158.272-47.268-158.272-130.792 0-48.424 26.06-92.292 67.434-115.836 38.745-22.05 28.999-80.788-15.022-88.919A257.936 257.936 0 0 0 279.135 0c-141.36 0-256 114.575-256 256 0 141.36 114.576 256 256 256zm0-464c12.985 0 25.689 1.201 38.016 3.478-54.76 31.163-91.693 90.042-91.693 157.554 0 113.848 103.641 199.2 215.252 177.944C402.574 433.964 344.366 464 279.135 464c-114.875 0-208-93.125-208-208s93.125-208 208-208z"></path></svg>

    <svg width="50px" height="50px" class="theme-toggle-light" alt="Icon used for changing site theme to light" onclick="ToggleTheme()" aria-hidden="true" focusable="false" data-prefix="far" data-icon="sun" class="svg-inline--fa fa-sun fa-w-16" role="img" xmlns="http://www.w3.org/2000/svg" viewBox="0 0 512 512"><path fill="currentColor" d="M494.2 221.9l-59.8-40.5 13.7-71c2.6-13.2-1.6-26.8-11.1-36.4-9.6-9.5-23.2-13.7-36.2-11.1l-70.9 13.7-40.4-59.9c-15.1-22.3-51.9-22.3-67 0l-40.4 59.9-70.8-13.7C98 60.4 84.5 64.5 75 74.1c-9.5 9.6-13.7 23.1-11.1 36.3l13.7 71-59.8 40.5C6.6 229.5 0 242 0 255.5s6.7 26 17.8 33.5l59.8 40.5-13.7 71c-2.6 13.2 1.6 26.8 11.1 36.3 9.5 9.5 22.9 13.7 36.3 11.1l70.8-13.7 40.4 59.9C230 505.3 242.6 512 256 512s26-6.7 33.5-17.8l40.4-59.9 70.9 13.7c13.4 2.7 26.8-1.6 36.3-11.1 9.5-9.5 13.6-23.1 11.1-36.3l-13.7-71 59.8-40.5c11.1-7.5 17.8-20.1 17.8-33.5-.1-13.6-6.7-26.1-17.9-33.7zm-112.9 85.6l17.6 91.2-91-17.6L256 458l-51.9-77-90.9 17.6 17.6-91.2-76.8-52 76.8-52-17.6-91.2 91 17.6L256 53l51.9 76.9 91-17.6-17.6 91.1 76.8 52-76.8 52.1zM256 152c-57.3 0-104 46.7-104 104s46.7 104 104 104 104-46.7 104-104-46.7-104-104-104zm0 160c-30.9 0-56-25.1-56-56s25.1-56 56-56 56 25.1 56 56-25.1 56-56 56z"></path></svg>

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