Consider using arrow functions for callbacks JS-0241
Anti-pattern
Minor
5 months ago
—
2 years old
Unexpected function expression
4652 return null == n
4653 ? null
4654 : Array.isArray(n)
4655 ? S.map(n, function (e) { 4656 return { name: t.name, value: e.replace(Et, "\r\n") }; 4657 }) 4658 : { name: t.name, value: n.replace(Et, "\r\n") };
4659 })
4660 .get();Unexpected function expression
4375 : "number" == typeof t
4376 ? (t += "")
4377 : Array.isArray(t) &&
4378 (t = S.map(t, function (e) { 4379 return null == e ? "" : e + ""; 4380 })), 4381 ((r =
4382 S.valHooks[this.type] ||
4383 S.valHooks[this.nodeName.toLowerCase()]) &&Unexpected function expression
1590 return (e === n) !== r;
1591 })
1592 : "string" != typeof n
1593 ? S.grep(e, function (e) { 1594 return -1 < i.call(n, e) !== r; 1595 }) 1596 : S.filter(n, e, r);
1597 }
1598 (S.filter = function (e, t, n) {Unexpected function expression
1586 return !!n.call(e, t, e) !== r;
1587 })
1588 : n.nodeType
1589 ? S.grep(e, function (e) { 1590 return (e === n) !== r; 1591 }) 1592 : "string" != typeof n
1593 ? S.grep(e, function (e) {
1594 return -1 < i.call(n, e) !== r;Unexpected function expression
1063 : 1 < a.length
1064 ? ((t = [e, e, "", o]),
1065 b.setFilters.hasOwnProperty(e.toLowerCase())
1066 ? le(function (e, t) { 1067 var n, 1068 r = a(e, o), 1069 i = r.length; 1070 while (i--) e[(n = P(e, r[i]))] = !(t[n] = r[i]); 1071 }) 1072 : function (e) {
1073 return a(e, 0, t);
1074 })
Description
It is recommended to use arrow functions as callbacks.
Arrow functions can be an attractive alternative to function expressions for callbacks or function arguments.
For example, arrow functions are automatically bound to their surrounding scope/context. This provides an alternative to the pre-ES6 standard of explicitly binding function expressions to achieve similar behavior.
Additionally, arrow functions are:
less verbose, and easier to reason about.
bound lexically regardless of where or when they are invoked.
Bad Practice
func(function(a) { return a; }); // ERROR
// prefer: func(a => a)
func(function() { return this.a; }.bind(this)); // ERROR
// prefer: func(() => this.a)
Recommended
// arrow function callback
func(a => a); // OK
// generator as callback
func(function*() { yield; }); // OK
// function expression not used as callback or function argument
var funcVar = function func(a) { return a; }; // OK
// unbound function expression callback
func(function() { return this.a; }); // OK
// recursive named function callback
func(function recursiveFunc(n) { return n && n + recursiveFunc(n - 1); }); // OK