1.js

var x = '/x/';
/x/==x

2.js

var calls = 0;

function x() {
  return (++calls % 6) > 0 ? x : true;
};

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

3.js

var x = {
  n: 0,
  valueOf: function() {
    return ++this.n % 2 ? 3 : 1;
  }
}

x > 2 && x < 2

4.js

var fn = function() {
  this.a = 'qwe';
};

fn.prototype.a = true;

var x = new fn();

delete x.a && x.a;

5.js

var x = {
  foo: 'foo',
  toString: function() {
    return 'foo';
  }
}

x[x]==x

6.js

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

typeof new x < typeof x

7.js

var x = {
  n: 0,
  valueOf: function() {
    return (++this.n % 2) ? 1 : -1;
  }
}

x - 1 === x + 1