053-training-js-7-if-else-and-ternary-operator.js

// In javascript, if..else is the most basic condition statement, it consists of three parts:condition, statement1, statement2, like this:

// if (condition) statementa
// else           statementb
// It means that if the condition is true, then execute the statementa, otherwise execute the statementb.If the statementa or statementb more than one line, you need to add { and } at the head and tail of statement in JS, to keep the same indentation on Python and to put a end in Ruby where it indeed ends.

// An example, if we want to judge whether a number is odd or even, we can write code like this:

// function oddEven(n){
//   if (n%2==1) return "odd number";
//   else        return "even number";
// }
// If there is more than one condition to judge, we can use the compound if...else statement. an example:

// function oldYoung(age){
//   if (age<16)      return "children"
//   else if (age<50) return "young man"   //use "else if" if needed
//   else             return "old man"
// }
// This function returns a different value depending on the parameter age.

// Looks very complicated? Well, JS and Ruby also support the ternary operator and Python has something similar too:

// condition ? statementa : statementb
// Condition and statement separated by "?", different statement separated by ":" in both Ruby and JS; in Python you put the condition in the middle of two alternatives. The two examples above can be simplified with ternary operator:

// function oddEven(n){
//   return n%2==1 ? "odd number" : "even number";
// }
// function oldYoung(age){
//   return age<16 ? "children" : age<50 ? "young man" : "old man";
// }
// #Task Complete function saleHotdogs, function accept 1 parameters:n, n is the number of customers to buy hotdogs, different numbers have different prices (refer to the following table), return a number that the customer need to pay how much money.

// +---------------+-------------+
// |  numbers n    | price(cents)|
// +---------------+-------------+
// |n<5            |    100      |
// +---------------+-------------+
// |n>=5 and n<10  |     95      |
// +---------------+-------------+
// |n>=10          |     90      |
// +---------------+-------------+
// You can use if..else or ternary operator to complete it.

function saleHotdogs(n){
  return n < 5 ? n * 100 : (n >= 5 && n < 10 ? n * 95 : n * 90)
}