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<main>
<h1>Prevent numeric form input invalidity</h1>
<p>Prevent illegal input while entering numbers into form fields which perform real-time calculations.</p>
<p>Behaviour update for the <a href="https://websemantics.uk/tools/convert-pixel-point-em-rem-percent/" target=_blank title="[new window]">Font-size converter</a> on webSemantics.</p>
<form class=frm aria-labelledby=frm_ttl>
<h2 id=frm_ttl class=-visually-hidden>Font-size conversion calculator</h2>
<div class=frm_fld-root>
<label class=frm_lbl-root>
<span class=lbl_txt>Browser default font-size </span>
<span class=-nowrap>
<input class=IN-rootFS type=number>
px
</span>
</label>
</div>
<div class=frm_fld-convert>
<label class=frm_lbl>
<span class=lbl_txt>Convert<span class=-visually-hidden> font-size</span></span>
<input class=IN-fromFS type=text data-allowNegative>
</label>
<fieldset class=frm_set>
<legend class=-visually-hidden>From:</legend>
<label class=IN_lbl-radio>
<span class=lbl_txt>px</span>
<input class="IN_radio-from" type=radio name=unitFrom id=IN_radio_from-px value=px>
<span></span>
</label>
<label class=IN_lbl-radio>
<span class=lbl_txt>%</span>
<input class="IN_radio-from" type=radio name=unitFrom id=IN_radio_from-percent value=percent>
<span></span>
</label>
<label class=IN_lbl-radio>
<span class=lbl_txt>pt</span>
<input class="IN_radio-from" type=radio name=unitFrom id=IN_radio_from-pt value=pt>
<span></span>
</label>
<label class=IN_lbl-radio>
<span class=lbl_txt>rem</span>
<input class="IN_radio-from" type=radio name=unitFrom id=IN_radio_from-rem value=rem checked>
<span></span>
</label>
</fieldset>
</div>
<div class=frm_fld-result>
<label class=frm_lbl aria-live=polite>
<span class=lbl_txt>Result</span>
<input class=IN-toFS type=text readonly>
<span class="IN_toUnit -visually-hidden">REM</span>
</label>
<fieldset class=frm_set>
<legend class=-visually-hidden>Change result unit to:</legend>
<label class=IN_lbl-radio>
<span class=lbl_txt>px</span>
<input class=IN_radio-to type=radio name=unitTo id=IN_radio_to-px value=px checked>
<span></span>
</label>
<label class=IN_lbl-radio>
<span class=lbl_txt>%</span>
<input class=IN_radio-to type=radio name=unitTo id=IN_radio_to-percent value=percent>
<span></span>
</label>
<label class=IN_lbl-radio>
<span class=lbl_txt>pt</span>
<input class=IN_radio-to type=radio name=unitTo id=IN_radio_to-pt value=pt>
<span></span>
</label>
<label class=IN_lbl-radio>
<span class=lbl_txt>rem</span>
<input class=IN_radio-to type=radio name=unitTo id=IN_radio_to-rem value=rem>
<span></span>
</label>
</fieldset>
</div>
<div style=text-align:right aria-live=polite>
[<span id=svg_from></span> = <span id=svg_to></span>]
— Version 5.0
</div>
</form>
<p>Try typing into the <i>Convert</i> field. See how the <i>Result</i> is updated live, as you type, but only while the <i>Convert</i> value is valid. Test starting with a period (.) or lead zero, or a zero after a period.</p>
<p><b>Updated November 2021</b> to replace <code>event.which</code> keyboard detection, and also to allow negative mumbers. Test adding a minus at the front, middle, end, with and without period.</p>
<p>If I've done it correctly, it should be impossible to enter invalid characters, or break the calculation.</p>
</main>
<!-- Footer codepen include -->
[[[https://codepen.io/2kool2/pen/mKeeGM]]]
/* Generic styling */
*, *::after, *::before {box-sizing: inherit;}
body {
--color: hsl(269, 19%, 30%);
--bgColor: hsla(32,100%,85%,.35);
--linkColor: hsla(214, 71%, 47%, 1);
--linkColorUnderline: hsla(214, 71%, 47%, .5);
--linkColorHover: hsla(214, 100%, 35%, 1);
--linkBgHover: hsla(214, 100%, 85%, 1);
--linkFocus: hsla(214, 71%, 80%, 0.3);
--focusOutline: hsla(214, 71%, 85%, 1);
--textShadow: #fff;
--boxShadow: hsla(0,0%,0%,.3);
--bgColorForm: hsla(120,50%,50%,.075);
font-family: sans-serif;
text-rendering: optimizeLegibility;
margin: 1rem;
line-height: 1.5;
padding-bottom: 2rem;
background-attachment: fixed;
background-image: url("data:image/svg+xml;charset=utf8,%3Csvg xmlns='http://www.w3.org/2000/svg'%3E%3Cdefs%3E%3Cfilter id='a'%3E%3CfeTurbulence type='fractalNoise' baseFrequency='.4'/%3E%3C/filter%3E%3C/defs%3E%3Crect filter='url(%23a)' opacity='.3' width='100%25' height='100%25'/%3E%3C/svg%3E");
min-height: 100%;
color: var(--color);
background-color: var(--bgColor);
}
main {
max-width: 34rem;
margin: 0 auto;
}
h1 {
font-weight: 100;
margin-top: 2rem;
margin-bottom: 1rem;
text-align: center;
}
h1 + p {
font-size: 1.35rem;
font-weight: 100;
text-align: center;
}
a:link,
a:visited {
color: var(--linkColor);
text-decoration-color: var(--linkColorUnderline);
outline: hsla(214, 71%, 80%, 0); solid .25rem;
transition:
color .3s ease-out,
background-color .3s ease-out,
outline-color .3s ease-out;
}
a:hover,
a:focus {
color: var(--linkColorHover);
outline: var(--linkBgHover) solid .25rem;
background-color: var(--linkBgHover);
}
i {
margin-right: .125em;
}
.-visually-hidden {
position: absolute !important;
clip: rect(1px,1px,1px,1px);
padding: 0 !important;
border: 0 !important;
height: 1px !important;
width: 1px !important;
overflow: hidden;
}
.-nowrap {
white-space: nowrap;
}
/* Not trying to redo my sites layout but a little neatness doesn't hurt */
.frm {
background-color: var(--bgColorForm);
border: 2px dashed #f90;
padding: .6rem 1rem 1rem;
max-width: 40rem;
margin: 0 auto;
line-height: 2;
}
.IN-fromFS {
margin-right: 1rem;
}
.IN-toFS {
margin-right: 1rem;
}
.frm_lbl > .lbl_txt {
display: inline-block;
min-width: 4rem;
}
.frm_set {
border: 0;
}
[class^="IN_radio"] {
margin-right: 1rem;
}
input[type="text"]:invalid + .validity:after {
color: red;
content: '✖';
}
input[type="text"]:valid + .validity:after {
color: green;
content: '✓';
}
.frm_set {
display: inline-block;
}
var supportsES6 = (function() {
// https://gist.github.com/bendc/d7f3dbc83d0f65ca0433caf90378cd95
try {
new Function('(a = 0) => a');
return true;
}
catch (err) {
return false;
}
}());
console.clear();
// Restricts input for the given textbox to the given inputFilter function.
// https://stackoverflow.com/questions/469357/html-text-input-allow-only-numeric-input
function setInputFilter(textbox, inputFilter) {
["input", "keydown", "keyup", "mousedown", "mouseup", "select", "contextmenu", "drop"].forEach(function(event) {
textbox.addEventListener(event, function() {
if (inputFilter(this.value)) {
this.oldValue = this.value;
this.oldSelectionStart = this.selectionStart;
this.oldSelectionEnd = this.selectionEnd;
} else if (this.hasOwnProperty("oldValue")) {
this.value = this.oldValue;
this.setSelectionRange(this.oldSelectionStart, this.oldSelectionEnd);
} else {
this.value = "";
}
});
});
}
// setInputFilter(document.getElementById("input"), function(value) {
// return /^[-]?\d*\.?\d*$/.test(value); // Allow digits and '.' only, using a RegExp
// });
var Convert_Font_Sizes = (function (window, document, supportsES6) {
'use strict';
if (!supportsES6) return;
const toUnit = document.querySelector('.IN_toUnit');
const radiosFrom = document.querySelectorAll('.IN_radio-from');
const radiosTo = document.querySelectorAll('.IN_radio-to');
// Limit to four rounded decimal places.
const sanitize = value => Math.round(value * 10000) / 10000;
const setValue = (value, prop, valueWhenIllegal) => {
value = sanitize(value);
// if (isNaN(value) || value === 0) value = valueWhenIllegal;
if (isNaN(value)) value = valueWhenIllegal;
inputs[prop].set(value); // string
};
const setInputEvents = prop => {
const obj = inputs[prop].obj;
obj.addEventListener('change', e => {
setValue(e.target.value, prop, 1);
});
obj.addEventListener('input', e => {
// Automatically updates valid values as they are typed
const target = e.target;
const value = target.value;
const length = value.length;
const lastChar = value.substr(length - 1);
const firstChar = value.charAt(0);
// Do not update values which detract from typing numbers
// No update when:
if (length === 0) return;
// if (value === '0') return;
if (lastChar === '.') return;
if (lastChar === '-' && lastChar === firstChar) return;
if (lastChar === '0' && value.indexOf('.') !== -1) return;
setValue(value, prop, 1);
});
inputs[prop].set(inputs[prop].value);
};
const setInputValues = (prop, value) => {
inputs[prop].obj.value = value;
inputs[prop].value = value;
updateResult();
};
const setRadioEvents = (radios, prop) => {
for (const rad of radios) {
rad.addEventListener('click', e => {
inputs[prop].set(e.target.value);
});
}
};
const setRadioValues = (prop, value) => {
inputs[prop].previousValue = inputs[prop].value;
inputs[prop].value = value;
if (toUnit) toUnit.textContent = inputs.unitsTo.value;
updateResult();
};
const inputs = {
rootFS : {
obj : document.querySelector('.IN-rootFS'),
value : 16,
init : _ => setInputEvents('rootFS'),
set : value => setInputValues('rootFS', value)
},
fromFS : {
obj : document.querySelector('.IN-fromFS'),
value : 16,
init : _ => setInputEvents('fromFS'),
set : value => setInputValues('fromFS', value)
},
toFS : {
obj : document.querySelector('.IN-toFS'),
value : 1,
init : _ => {},
set : value => {
// Prevents infinite recursion
if (value !== parseFloat(inputs.toFS.obj.value)) {
setInputValues('toFS', value);
}
}
},
unitsFrom : {
value : 'rem',
previousValue : 'rem',
init : _ => setRadioEvents(radiosFrom, 'unitsFrom'),
set : value => setRadioValues('unitsFrom', value)
},
unitsTo : {
value : 'px',
previousValue : 'px',
init : _ => setRadioEvents(radiosTo, 'unitsTo'),
set : value => setRadioValues('unitsTo', value)
}
};
const updateResult = _ => {
const from = inputs.fromFS.value;
const root = inputs.rootFS.value;
// Convert From value into pixels
let pix = 0;
switch(inputs.unitsFrom.value) {
case 'px' :
pix = from;
break;
case 'pt' :
pix = from * 96 / 72;
break;
case 'percent' :
pix = from * root / 100;
break;
case 'rem' :
pix = from * root;
break;
}
// Sets Result value
switch (inputs.unitsTo.value) {
case 'px' :
pix = pix;
break;
case 'pt' :
pix = pix * 72 / 96;
break;
case 'percent' :
pix = pix * 100 / root;
break;
case 'rem' :
pix = pix / root;
break;
}
setValue(pix, 'toFS', 1);
};
// Open input settings and for each primary, run init
const initialise = _ => {
// Object.keys(inputs).forEach(key => inputs[key].init());
Object.values(inputs).forEach(prop => prop.init());
// Required to reset CSS ticks on page refresh
const checked = document.querySelectorAll('[class^="IN_radio"]:checked');
for (const chkd of checked) chkd.click();
};
initialise();
}(window, document, supportsES6));
// (Simulated) Update SVG calculator values (purely for the visual)
var Update_Svg_Calculator = (function (window, document, supportsES6) {
'use strict';
if (!supportsES6) return;
const root_fs = document.querySelector('.IN-rootFS');
const from_fs = document.querySelector('.IN-fromFS');
const to_fs = document.querySelector('.IN-toFS');
if (!(root_fs && from_fs && to_fs)) return;
const radios = document.querySelectorAll('[class^="IN_radio-"]');
if (!radios) return;
// Limit to three rounded decimal places.
const sanitize = value => Math.round(value * 1000) / 1000;
const setSVG = _ => {
const value = {
from : from_fs.value,
to : to_fs.value
}
const set = key => {
const txtObj = document.getElementById('svg_' + key);
if (!txtObj) return;
const selector = `.IN_radio-${key}:checked`;
const unitObj = document.querySelector(selector);
if (!unitObj) return;
const unit = unitObj.value === 'percent' ? '%' : unitObj.value;
txtObj.textContent = sanitize(value[key]) + unit;
}
Object.keys(value).forEach(key => set(key));
};
const init = _ => {
root_fs.addEventListener('input', setSVG);
from_fs.addEventListener('input', setSVG);
to_fs.addEventListener('input', setSVG);
for (const rad of radios) {
rad.addEventListener('click', setSVG);
}
setSVG();
};
init();
}(window, document, supportsES6));
Also see: Tab Triggers