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types.js
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types.js
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var myName;
myName = "Nizar";
myName = "Dapper Dan";
// These error because "myName" is supposed to be a string
// myName = 99;
// myName = [];
// name type value
// | | |
var blah = 42;
blah = 99;
// These error because "blah" is supposed to be a number
// blah = "hello?";
// blah = true;
var isHungry = true;
isHungry = Boolean(1);
// Use "any" sparingly because it defeats the purpose of TypeScript.
var x = {};
x = true;
x = "hello";
// you can declare the type of things inside an array
var myArray1 = [];
var myArray2 = ["thor", "scarlet witch"];
myArray1.push("hot dog", "pizza", "banana smoothie");
// Error because "myArray1" can only contain strings
// myArray1.push(99);
// "x" must be a number
// |
function quadruple(x) {
// |
return x * x * x * x; // "quadruple()" must return a number
}
console.log(quadruple(20));
// Errors because the "x" parameter must be a number
// console.log( quadruple("sup") );
// "myNumbers" must be an array of numbers
// |
function calculateAverage(myNumbers) {
var total = 0;
myNumbers.forEach(function (x) {
total += x;
});
return total / myNumbers.length;
}
var names = ["a", "b", "c"];
var myTestScores = [85, 73, 57, 100];
console.log(calculateAverage(myTestScores));
// Errors because "names" is an array of strings
// console.log( calculateAverage(names) );