[javascript] jQuery click / toggle between two functions

Micro jQuery Plugin

If you want your own chainable clickToggle jQuery Method you can do it like:

jQuery.fn.clickToggle = function(a, b) {_x000D_
  return this.on("click", function(ev) { [b, a][this.$_io ^= 1].call(this, ev) })_x000D_
};_x000D_
_x000D_
// TEST:_x000D_
$('button').clickToggle(function(ev) {_x000D_
  $(this).text("B"); _x000D_
}, function(ev) {_x000D_
  $(this).text("A");_x000D_
});

<button>A</button>_x000D_
<button>A</button>_x000D_
<button>A</button>_x000D_
_x000D_
<script src="//code.jquery.com/jquery-3.3.1.min.js"></script>

Simple Functions Toggler

LIVE DEMO

function a(){ console.log('a'); }
function b(){ console.log('b'); }

$("selector").click(function() { 
  return (this.tog = !this.tog) ? a() : b();
});

If you want it even shorter (why would one, right?!) you can use the Bitwise XOR ^*Docs operator like:
DEMO

  return (this.tog^=1) ? a() : b();

That's all.
_{The trick is to set to the this Object a boolean property tog, and toggle it using negation (tog = !tog)
and put the needed function calls in a Conditional Operator ?:}

In OP's example (even with multiple elements) could look like:

function a(el){ $(el).animate({width: 260}, 1500); }
function b(el){ $(el).animate({width: 30}, 1500);  }

$("selector").click(function() {
  var el = this;
  return (el.t = !el.t) ? a(el) : b(el);
}); 

ALSO: You can also store-toggle like:
DEMO:

$("selector").click(function() {
  $(this).animate({width: (this.tog ^= 1) ? 260 : 30 });
}); 

_{but it was not the OP's exact request for he's looking for a way to have two separate operations / functions}

Using Array.prototype.reverse:

_{Note: this will not store the current Toggle state but just inverse our functions positions in Array (It has it's uses...)}

You simply store your a,b functions inside an array, onclick you simply reverse the array order and execute the array[1] function:

LIVE DEMO

function a(){ console.log("a"); }
function b(){ console.log("b"); }
var ab = [a,b];

$("selector").click(function(){
  ab.reverse()[1](); // Reverse and Execute! // >> "a","b","a","b"...
});

SOME MASHUP!

jQuery DEMO
JavaScript DEMO

Create a nice function toggleAB() that will contain your two functions, put them in Array, and at the end of the array you simply execute the function [0 // 1] respectively depending on the tog property that's passed to the function from the this reference:

function toggleAB(){
  var el = this; // `this` is the "button" Element Obj reference`
  return [
    function() { console.log("b"); },
    function() { console.log("a"); }
  ][el.tog^=1]();
}

$("selector").click( toggleAB );