var _ = R; /***************************************** C U R R Y I N G E X A M P L E ******************************************/ // We‘ve got a nice multiply function. // It takes two arguments. console.log( _.multiply(3, 4) ); // But it has been secretly curried already // so we can feed it fewer arguments and it // will return a new function. // // How about making a function to double a // value? Done. var double = _.multiply(2); console.log( double(13) ); /***************************************** Y O U R T U R N ******************************************/ // _.split pulls a string apart around a // given value console.log( _.split(‘i‘, ‘mississippi‘) ); // -- Challenge 1 ------------------------ // Make a function called "words" which // returns a list of words in a string. // Use only the split function and // currying. console.log("Testing challenge 1..."); var words = _.split(‘ ‘); // change this assertEqualArrays( [‘one‘, ‘two‘, ‘three‘], words(‘one two three‘) ); console.log("passed"); // -- Challenge 2 ------------------------ // Create a function to triple every // number in a list using only // _.multiply and _.map. console.log("Testing challenge 2..."); var tripleList = _.map(_.multiply(3)); assertEqualArrays([3,6,9], tripleList([1,2,3])); console.log("passed"); // -- Challenge 3 ------------------------ // Create a function to find the largest // number in a list. You can use the // greater(a,b) function which returns the // greater of its two inputs. You can do // this with currying and one of the list // functions _.map, _.filter, or _.reduce. console.log("Testing challenge 3..."); var greater = function(a,b) { return a > b ? a : b; }; var max = _.reduce(greater, -Infinity); assertEqual(9, max([1,-3483,9,7,2])); assertEqual(-1, max([-21,-3483,-2,-1])); console.log("passed"); console.log("All tests pass."); /****************************************** B A C K G R O U N D C O D E *******************************************/ function assertEqualArrays(x,y) { if(x.length !== y.length) throw("expected "+x+" to equal "+y); for(var i in x) { if(x[i] !== y[i]) { throw("expected "+x+" to equal "+y); } } } function assertEqual(x,y){ if(x !== y) throw("expected "+x+" to equal "+y); }
时间: 2024-12-23 01:31:37