--- /dev/null
+/**
+ * @class jQuery.plugin.byteLimit
+ */
+( function ( $ ) {
+
+ var eventKeys = [
+ 'keyup.byteLimit',
+ 'keydown.byteLimit',
+ 'change.byteLimit',
+ 'mouseup.byteLimit',
+ 'cut.byteLimit',
+ 'paste.byteLimit',
+ 'focus.byteLimit',
+ 'blur.byteLimit'
+ ].join( ' ' );
+
+ /**
+ * Utility function to trim down a string, based on byteLimit
+ * and given a safe start position. It supports insertion anywhere
+ * in the string, so "foo" to "fobaro" if limit is 4 will result in
+ * "fobo", not "foba". Basically emulating the native maxlength by
+ * reconstructing where the insertion occurred.
+ *
+ * @static
+ * @param {string} safeVal Known value that was previously returned by this
+ * function, if none, pass empty string.
+ * @param {string} newVal New value that may have to be trimmed down.
+ * @param {number} byteLimit Number of bytes the value may be in size.
+ * @param {Function} [fn] See jQuery#byteLimit.
+ * @return {Object}
+ * @return {string} return.newVal
+ * @return {boolean} return.trimmed
+ */
+ $.trimByteLength = function ( safeVal, newVal, byteLimit, fn ) {
+ var startMatches, endMatches, matchesLen, inpParts,
+ oldVal = safeVal;
+
+ // Run the hook if one was provided, but only on the length
+ // assessment. The value itself is not to be affected by the hook.
+ if ( $.byteLength( fn ? fn( newVal ) : newVal ) <= byteLimit ) {
+ // Limit was not reached, just remember the new value
+ // and let the user continue.
+ return {
+ newVal: newVal,
+ trimmed: false
+ };
+ }
+
+ // Current input is longer than the active limit.
+ // Figure out what was added and limit the addition.
+ startMatches = 0;
+ endMatches = 0;
+
+ // It is important that we keep the search within the range of
+ // the shortest string's length.
+ // Imagine a user adds text that matches the end of the old value
+ // (e.g. "foo" -> "foofoo"). startMatches would be 3, but without
+ // limiting both searches to the shortest length, endMatches would
+ // also be 3.
+ matchesLen = Math.min( newVal.length, oldVal.length );
+
+ // Count same characters from the left, first.
+ // (if "foo" -> "foofoo", assume addition was at the end).
+ while (
+ startMatches < matchesLen &&
+ oldVal.charAt( startMatches ) === newVal.charAt( startMatches )
+ ) {
+ startMatches += 1;
+ }
+
+ while (
+ endMatches < ( matchesLen - startMatches ) &&
+ oldVal.charAt( oldVal.length - 1 - endMatches ) === newVal.charAt( newVal.length - 1 - endMatches )
+ ) {
+ endMatches += 1;
+ }
+
+ inpParts = [
+ // Same start
+ newVal.slice( 0, startMatches ),
+ // Inserted content
+ newVal.slice( startMatches, newVal.length - endMatches ),
+ // Same end
+ newVal.slice( newVal.length - endMatches )
+ ];
+
+ // Chop off characters from the end of the "inserted content" string
+ // until the limit is statisfied.
+ if ( fn ) {
+ // stop, when there is nothing to slice - T43450
+ while ( $.byteLength( fn( inpParts.join( '' ) ) ) > byteLimit && inpParts[ 1 ].length > 0 ) {
+ inpParts[ 1 ] = inpParts[ 1 ].slice( 0, -1 );
+ }
+ } else {
+ while ( $.byteLength( inpParts.join( '' ) ) > byteLimit ) {
+ inpParts[ 1 ] = inpParts[ 1 ].slice( 0, -1 );
+ }
+ }
+
+ return {
+ newVal: inpParts.join( '' ),
+ // For pathological fn() that always returns a value longer than the limit, we might have
+ // ended up not trimming - check for this case to avoid infinite loops
+ trimmed: newVal !== inpParts.join( '' )
+ };
+ };
+
+ /**
+ * Enforces a byte limit on an input field, so that UTF-8 entries are counted as well,
+ * when, for example, a database field has a byte limit rather than a character limit.
+ * Plugin rationale: Browser has native maxlength for number of characters, this plugin
+ * exists to limit number of bytes instead.
+ *
+ * Can be called with a custom limit (to use that limit instead of the maxlength attribute
+ * value), a filter function (in case the limit should apply to something other than the
+ * exact input value), or both. Order of parameters is important!
+ *
+ * @param {number} [limit] Limit to enforce, fallsback to maxLength-attribute,
+ * called with fetched value as argument.
+ * @param {Function} [fn] Function to call on the string before assessing the length.
+ * @return {jQuery}
+ * @chainable
+ */
+ $.fn.byteLimit = function ( limit, fn ) {
+ // If the first argument is the function,
+ // set fn to the first argument's value and ignore the second argument.
+ if ( $.isFunction( limit ) ) {
+ fn = limit;
+ limit = undefined;
+ // Either way, verify it is a function so we don't have to call
+ // isFunction again after this.
+ } else if ( !fn || !$.isFunction( fn ) ) {
+ fn = undefined;
+ }
+
+ // The following is specific to each element in the collection.
+ return this.each( function ( i, el ) {
+ var $el, elLimit, prevSafeVal;
+
+ $el = $( el );
+
+ // If no limit was passed to byteLimit(), use the maxlength value.
+ // Can't re-use 'limit' variable because it's in the higher scope
+ // that would affect the next each() iteration as well.
+ // Note that we use attribute to read the value instead of property,
+ // because in Chrome the maxLength property by default returns the
+ // highest supported value (no indication that it is being enforced
+ // by choice). We don't want to bind all of this for some ridiculously
+ // high default number, unless it was explicitly set in the HTML.
+ // Also cast to a (primitive) number (most commonly because the maxlength
+ // attribute contains a string, but theoretically the limit parameter
+ // could be something else as well).
+ elLimit = Number( limit === undefined ? $el.attr( 'maxlength' ) : limit );
+
+ // If there is no (valid) limit passed or found in the property,
+ // skip this. The < 0 check is required for Firefox, which returns
+ // -1 (instead of undefined) for maxLength if it is not set.
+ if ( !elLimit || elLimit < 0 ) {
+ return;
+ }
+
+ if ( fn ) {
+ // Save function for reference
+ $el.data( 'byteLimit.callback', fn );
+ }
+
+ // Remove old event handlers (if there are any)
+ $el.off( '.byteLimit' );
+
+ if ( fn ) {
+ // Disable the native maxLength (if there is any), because it interferes
+ // with the (differently calculated) byte limit.
+ // Aside from being differently calculated (average chars with byteLimit
+ // is lower), we also support a callback which can make it to allow longer
+ // values (e.g. count "Foo" from "User:Foo").
+ // maxLength is a strange property. Removing or setting the property to
+ // undefined directly doesn't work. Instead, it can only be unset internally
+ // by the browser when removing the associated attribute (Firefox/Chrome).
+ // https://bugs.chromium.org/p/chromium/issues/detail?id=136004
+ $el.removeAttr( 'maxlength' );
+
+ } else {
+ // If we don't have a callback the bytelimit can only be lower than the charlimit
+ // (that is, there are no characters less than 1 byte in size). So lets (re-)enforce
+ // the native limit for efficiency when possible (it will make the while-loop below
+ // faster by there being less left to interate over).
+ $el.attr( 'maxlength', elLimit );
+ }
+
+ // Safe base value, used to determine the path between the previous state
+ // and the state that triggered the event handler below - and enforce the
+ // limit approppiately (e.g. don't chop from the end if text was inserted
+ // at the beginning of the string).
+ prevSafeVal = '';
+
+ // We need to listen to after the change has already happened because we've
+ // learned that trying to guess the new value and canceling the event
+ // accordingly doesn't work because the new value is not always as simple as:
+ // oldValue + String.fromCharCode( e.which ); because of cut, paste, select-drag
+ // replacements, and custom input methods and what not.
+ // Even though we only trim input after it was changed (never prevent it), we do
+ // listen on events that input text, because there are cases where the text has
+ // changed while text is being entered and keyup/change will not be fired yet
+ // (such as holding down a single key, fires keydown, and after each keydown,
+ // we can trim the previous one).
+ // See https://www.w3.org/TR/DOM-Level-3-Events/#events-keyboard-event-order for
+ // the order and characteristics of the key events.
+ $el.on( eventKeys, function () {
+ var res = $.trimByteLength(
+ prevSafeVal,
+ this.value,
+ elLimit,
+ fn
+ );
+
+ // Only set value property if it was trimmed, because whenever the
+ // value property is set, the browser needs to re-initiate the text context,
+ // which moves the cursor at the end the input, moving it away from wherever it was.
+ // This is a side-effect of limiting after the fact.
+ if ( res.trimmed === true ) {
+ this.value = res.newVal;
+ // Trigger a 'change' event to let other scripts attached to this node know that the value
+ // was changed. This will also call ourselves again, but that's okay, it'll be a no-op.
+ $el.trigger( 'change' );
+ }
+ // Always adjust prevSafeVal to reflect the input value. Not doing this could cause
+ // trimByteLength to compare the new value to an empty string instead of the
+ // old value, resulting in trimming always from the end (T42850).
+ prevSafeVal = res.newVal;
+ } );
+ } );
+ };
+
+ /**
+ * @class jQuery
+ * @mixins jQuery.plugin.byteLimit
+ */
+}( jQuery ) );
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