You should use map and sort methods.
First of all, you can generate a random number for every item in the array, using Math.random method. Next step is to sort array by this generated number.
Last step is to create the sentence with the items of the array, using join method.
var array1 = ["The", "Man", "and", "his", "dog"];
console.log(array1.map(function(n){
return [Math.random(), n];
}).sort().map(function(item){
return item[1] ;
}).join(' '));