1.js

var x = '/x/';

/x/==x

2.js

var x = function () {
    var i = -5; 
    return x = function () {
        return ++i ? x : true;
    };
};

x() === x()() === x()()()

3.js

var x = {
   x: 5,
   toString: function () {
       this.x -= 2;
       return this.x;
   }
};

x > 2 && x < 2

4.js

var X = function () {
    this.a = true;
};
X.prototype.a = true;
var x = new X;

delete x.a && x.a;

5.js

var x = {
    "[object Object]": "[object Object]"
};

x[x]==x

6.js

var x = function () { x = '' };

typeof new x < typeof x

7.js

var x = Infinity;

x - 1 === x + 1