diff --git a/components/prism-javascript.js b/components/prism-javascript.js
index f215e5eb16..240dcfecce 100644
--- a/components/prism-javascript.js
+++ b/components/prism-javascript.js
@@ -19,7 +19,7 @@ Prism.languages.insertBefore('javascript', 'keyword', {
 	},
 	'parameter': [
 		{
-			pattern: /(function(?:\s+[_$a-z\xA0-\uFFFF][$\w\xA0-\uFFFF]*)?\s*\(\s*)\S[^()]*(?=\s*\))/,
+			pattern: /(function(?:\s+[_$a-z\xA0-\uFFFF][$\w\xA0-\uFFFF]*)?\s*\(\s*)[^\s()][^()]*?(?=\s*\))/,
 			lookbehind: true,
 			inside: Prism.languages.javascript
 		},
@@ -28,12 +28,12 @@ Prism.languages.insertBefore('javascript', 'keyword', {
 			inside: Prism.languages.javascript
 		},
 		{
-			pattern: /(\()[^()]+(?=\)\s*=>)/,
+			pattern: /(\(\s*)[^\s()][^()]*?(?=\s*\)\s*=>)/,
 			lookbehind: true,
 			inside: Prism.languages.javascript
 		},
 		{
-			pattern: /(\b(?!await|delete|export|for|if|new|return|switch|throw|typeof|while|yield)(?:[_$a-z\xA0-\uFFFF][$\w\xA0-\uFFFF]*\s*)\(\s*)\S[^()]*(?=\s*\)\s*\{)/,
+			pattern: /((?:\b|\s|^)(?!(?:await|delete|export|for|if|new|return|switch|throw|typeof|while|yield)(?![$\w\xA0-\uFFFF]))(?:[_$a-z\xA0-\uFFFF][$\w\xA0-\uFFFF]*\s*)\(\s*)[^\s()][^()]*?(?=\s*\)\s*\{)/,
 			lookbehind: true,
 			inside: Prism.languages.javascript
 		}
diff --git a/components/prism-javascript.min.js b/components/prism-javascript.min.js
index 734d150929..4ff8ffca7e 100644
--- a/components/prism-javascript.min.js
+++ b/components/prism-javascript.min.js
@@ -1 +1 @@
-Prism.languages.javascript=Prism.languages.extend("clike",{keyword:/\b(?:as|async|await|break|case|catch|class|const|continue|debugger|default|delete|do|else|enum|export|extends|finally|for|from|function|get|if|implements|import|in|instanceof|interface|let|new|null|of|package|private|protected|public|return|set|static|super|switch|this|throw|try|typeof|var|void|while|with|yield)\b/,number:/\b(?:0[xX][\dA-Fa-f]+|0[bB][01]+|0[oO][0-7]+|NaN|Infinity)\b|(?:\b\d+\.?\d*|\B\.\d+)(?:[Ee][+-]?\d+)?/,"function":/[_$a-z\xA0-\uFFFF][$\w\xA0-\uFFFF]*(?=\s*\()/i,operator:/-[-=]?|\+[+=]?|!=?=?|<<?=?|>>?>?=?|=(?:==?|>)?|&[&=]?|\|[|=]?|\*\*?=?|\/=?|~|\^=?|%=?|\?|\.{3}/}),Prism.languages.insertBefore("javascript","keyword",{regex:{pattern:/((?:^|[^$\w\xA0-\uFFFF."'\])\s])\s*)\/(\[[^\]\r\n]+]|\\.|[^\/\\\[\r\n])+\/[gimyu]{0,5}(?=\s*($|[\r\n,.;})\]]))/,lookbehind:!0,greedy:!0},"function-variable":{pattern:/[_$a-z\xA0-\uFFFF][$\w\xA0-\uFFFF]*(?=\s*=\s*(?:async(?:(?:\s*(?=\())|\s+))?(?:function\b|(?:\([^()]*\)|[_$a-z\xA0-\uFFFF][$\w\xA0-\uFFFF]*)\s*=>))/i,alias:"function"},parameter:[{pattern:/(function(?:\s+[_$a-z\xA0-\uFFFF][$\w\xA0-\uFFFF]*)?\s*\(\s*)\S[^()]*(?=\s*\))/,lookbehind:!0,inside:Prism.languages.javascript},{pattern:/[_$a-z\xA0-\uFFFF][$\w\xA0-\uFFFF]*(?=\s*=>)/,inside:Prism.languages.javascript},{pattern:/(\()[^()]+(?=\)\s*=>)/,lookbehind:!0,inside:Prism.languages.javascript},{pattern:/(\b(?!await|delete|export|for|if|new|return|switch|throw|typeof|while|yield)(?:[_$a-z\xA0-\uFFFF][$\w\xA0-\uFFFF]*\s*)\(\s*)\S[^()]*(?=\s*\)\s*\{)/,lookbehind:!0,inside:Prism.languages.javascript}],constant:/\b[A-Z][A-Z\d_]*\b/}),Prism.languages.insertBefore("javascript","string",{"template-string":{pattern:/`(?:\\[\s\S]|\${[^}]+}|[^\\`])*`/,greedy:!0,inside:{interpolation:{pattern:/\${[^}]+}/,inside:{"interpolation-punctuation":{pattern:/^\${|}$/,alias:"punctuation"},rest:null}},string:/[\s\S]+/}}}),Prism.languages.javascript["template-string"].inside.interpolation.inside.rest=Prism.languages.javascript,Prism.languages.markup&&Prism.languages.insertBefore("markup","tag",{script:{pattern:/(<script[\s\S]*?>)[\s\S]*?(?=<\/script>)/i,lookbehind:!0,inside:Prism.languages.javascript,alias:"language-javascript",greedy:!0}}),Prism.languages.js=Prism.languages.javascript;
\ No newline at end of file
+Prism.languages.javascript=Prism.languages.extend("clike",{keyword:/\b(?:as|async|await|break|case|catch|class|const|continue|debugger|default|delete|do|else|enum|export|extends|finally|for|from|function|get|if|implements|import|in|instanceof|interface|let|new|null|of|package|private|protected|public|return|set|static|super|switch|this|throw|try|typeof|var|void|while|with|yield)\b/,number:/\b(?:0[xX][\dA-Fa-f]+|0[bB][01]+|0[oO][0-7]+|NaN|Infinity)\b|(?:\b\d+\.?\d*|\B\.\d+)(?:[Ee][+-]?\d+)?/,"function":/[_$a-z\xA0-\uFFFF][$\w\xA0-\uFFFF]*(?=\s*\()/i,operator:/-[-=]?|\+[+=]?|!=?=?|<<?=?|>>?>?=?|=(?:==?|>)?|&[&=]?|\|[|=]?|\*\*?=?|\/=?|~|\^=?|%=?|\?|\.{3}/}),Prism.languages.insertBefore("javascript","keyword",{regex:{pattern:/((?:^|[^$\w\xA0-\uFFFF."'\])\s])\s*)\/(\[[^\]\r\n]+]|\\.|[^\/\\\[\r\n])+\/[gimyu]{0,5}(?=\s*($|[\r\n,.;})\]]))/,lookbehind:!0,greedy:!0},"function-variable":{pattern:/[_$a-z\xA0-\uFFFF][$\w\xA0-\uFFFF]*(?=\s*=\s*(?:async(?:(?:\s*(?=\())|\s+))?(?:function\b|(?:\([^()]*\)|[_$a-z\xA0-\uFFFF][$\w\xA0-\uFFFF]*)\s*=>))/i,alias:"function"},parameter:[{pattern:/(function(?:\s+[_$a-z\xA0-\uFFFF][$\w\xA0-\uFFFF]*)?\s*\(\s*)[^\s()][^()]*?(?=\s*\))/,lookbehind:!0,inside:Prism.languages.javascript},{pattern:/[_$a-z\xA0-\uFFFF][$\w\xA0-\uFFFF]*(?=\s*=>)/,inside:Prism.languages.javascript},{pattern:/(\(\s*)[^\s()][^()]*?(?=\s*\)\s*=>)/,lookbehind:!0,inside:Prism.languages.javascript},{pattern:/((?:\b|\s|^)(?!(?:await|delete|export|for|if|new|return|switch|throw|typeof|while|yield)(?![$\w\xA0-\uFFFF]))(?:[_$a-z\xA0-\uFFFF][$\w\xA0-\uFFFF]*\s*)\(\s*)[^\s()][^()]*?(?=\s*\)\s*\{)/,lookbehind:!0,inside:Prism.languages.javascript}],constant:/\b[A-Z][A-Z\d_]*\b/}),Prism.languages.insertBefore("javascript","string",{"template-string":{pattern:/`(?:\\[\s\S]|\${[^}]+}|[^\\`])*`/,greedy:!0,inside:{interpolation:{pattern:/\${[^}]+}/,inside:{"interpolation-punctuation":{pattern:/^\${|}$/,alias:"punctuation"},rest:null}},string:/[\s\S]+/}}}),Prism.languages.javascript["template-string"].inside.interpolation.inside.rest=Prism.languages.javascript,Prism.languages.markup&&Prism.languages.insertBefore("markup","tag",{script:{pattern:/(<script[\s\S]*?>)[\s\S]*?(?=<\/script>)/i,lookbehind:!0,inside:Prism.languages.javascript,alias:"language-javascript",greedy:!0}}),Prism.languages.js=Prism.languages.javascript;
\ No newline at end of file
diff --git a/prism.js b/prism.js
index 0b58a69534..b80de4637f 100644
--- a/prism.js
+++ b/prism.js
@@ -742,7 +742,7 @@ Prism.languages.insertBefore('javascript', 'keyword', {
 	},
 	'parameter': [
 		{
-			pattern: /(function(?:\s+[_$a-z\xA0-\uFFFF][$\w\xA0-\uFFFF]*)?\s*\(\s*)\S[^()]*(?=\s*\))/,
+			pattern: /(function(?:\s+[_$a-z\xA0-\uFFFF][$\w\xA0-\uFFFF]*)?\s*\(\s*)[^\s()][^()]*?(?=\s*\))/,
 			lookbehind: true,
 			inside: Prism.languages.javascript
 		},
@@ -751,12 +751,12 @@ Prism.languages.insertBefore('javascript', 'keyword', {
 			inside: Prism.languages.javascript
 		},
 		{
-			pattern: /(\()[^()]+(?=\)\s*=>)/,
+			pattern: /(\(\s*)[^\s()][^()]*?(?=\s*\)\s*=>)/,
 			lookbehind: true,
 			inside: Prism.languages.javascript
 		},
 		{
-			pattern: /(\b(?!await|delete|export|for|if|new|return|switch|throw|typeof|while|yield)(?:[_$a-z\xA0-\uFFFF][$\w\xA0-\uFFFF]*\s*)\(\s*)\S[^()]*(?=\s*\)\s*\{)/,
+			pattern: /((?:\b|\s|^)(?!(?:await|delete|export|for|if|new|return|switch|throw|typeof|while|yield)(?![$\w\xA0-\uFFFF]))(?:[_$a-z\xA0-\uFFFF][$\w\xA0-\uFFFF]*\s*)\(\s*)[^\s()][^()]*?(?=\s*\)\s*\{)/,
 			lookbehind: true,
 			inside: Prism.languages.javascript
 		}
diff --git a/tests/languages/javascript/class-method_feature.test b/tests/languages/javascript/class-method_feature.test
index a2e3ceaa7e..25d5992f9e 100644
--- a/tests/languages/javascript/class-method_feature.test
+++ b/tests/languages/javascript/class-method_feature.test
@@ -1,7 +1,8 @@
 class Test {
-	foo(x, y = 0) {}
-	async bar(x, y = 0) {}
-	_ ( ) {}
+	foo( x, y = 0) {}
+	async bar(x, y = 0 ) {}
+	$ ( ) {}
+	asyncFoo(){}
 }
 
 ----------------------------------------------------
@@ -38,7 +39,13 @@ class Test {
 	["punctuation", "{"],
 	["punctuation", "}"],
 
-	["function", "_"],
+	["function", "$"],
+	["punctuation", "("],
+	["punctuation", ")"],
+	["punctuation", "{"],
+	["punctuation", "}"],
+
+	["function", "asyncFoo"],
 	["punctuation", "("],
 	["punctuation", ")"],
 	["punctuation", "{"],
diff --git a/tests/languages/javascript/function-variable_feature.test b/tests/languages/javascript/function-variable_feature.test
index 8dbeb0aae8..d8b04ee38e 100644
--- a/tests/languages/javascript/function-variable_feature.test
+++ b/tests/languages/javascript/function-variable_feature.test
@@ -2,7 +2,7 @@ foo = function ( x, y) {}
 bar = async function baz (x ) {}
 baz = async(x) => x
 fooBar = x => x
-fooBar = (x, y) => x
+fooBar = ( x, y ) => x
 ಠ_ಠ = () => {}
 Ƞȡ_҇ = async (ಠ, Ƞ = 2) => {}
 
@@ -29,7 +29,7 @@ fooBar = (x, y) => x
 	["function", "baz"],
 	["punctuation", "("],
 	["parameter", [
-		"x "
+		"x"
 	]],
 	["punctuation", ")"],
 	["punctuation", "{"],