Type conversion
আমাদের দুই ধরনের type conversion রয়েছেঃ
1. Implicit type conversion.
2. Explicit type conversion .
#যে type conversion টা নিজে নিজে হয়ে যায় সেটা হলো implicit type conversion. আর explicit type conversion টা হলো আমরা নির্দিষ্ট করে বলে দিবো তুমি এই type এ convert হউ।
# আর যে type conversion আমরা নিজে নিজে করি , মানে হল আমরা জোর করে পরিবর্তন করে দেই সেইগুলো হলো Explicit type conversion.
*Example of implicit type conversion:
Example 1: Implicit Conversion to String
result = '3' + 2;
console.log(result) // "32"
result = '3' + true;
console.log(result); // "3true"
result = '3' + undefined;
console.log(result); // "3undefined"
result = '3' + null;
console.log(result); // "3null"
Example 2: Implicit Conversion to Number:
// numeric string used with - , / , * results number type
result = '4' - '2';
console.log(result); // 2
result = '4' - 2;
console.log(result); // 2
result = '4' * 2;
console.log(result); // 8
result = '4' / 2;
console.log(result); // 2
Example 3: Non-numeric String Results to NaN:
// non-numeric string used with - , / , * results to NaN
let result;
result = 'hello' - 'world';
console.log(result); // NaN
result = '4' - 'hello';
console.log(result); // NaN
Example 4: Implicit Boolean Conversion to Number:
// if boolean is used, true is 1, false is 0
let result;
result = '4' - true;
console.log(result); // 3
result = 4 + true;
console.log(result); // 5
result = 4 + false;
console.log(result); // 4
Example 5: null Conversion to Number
// null is 0 when used with number
let result;
result = 4 + null;
console.log(result); // 4
result = 4 - null;
console.log(result); // 4
Example 6: undefined used with number, boolean or null
// Arithmetic operation of undefined with number, boolean or null gives NaN
let result;
result = 4 + undefined;
console.log(result); // NaN
result = 4 - undefined;
console.log(result); // NaN
result = true + undefined;
console.log(result); // NaN
result = null + undefined;
console.log(result); // NaN
*Example of Explicit type conversion:
1. Convert to Number Explicitly
let result;
// string to number
result = Number('324');
console.log(result); // 324
result = Number('324e-1')
console.log(result); // 32.4
// boolean to number
result = Number(true);
console.log(result); // 1
result = Number(false);
console.log(result); // 0
In JavaScript, empty strings and
null values return 0. For example,let result;
result = Number(null);
console.log(result); // 0
let result = Number(' ')
console.log(result); // 0
If a string is an invalid number, the result will be
NaN. For example,let result;
result = Number(null);
console.log(result); // 0
let result = Number(' ')
console.log(result); // 0
If a string is an invalid number, the result will be
NaN. For example,let result;
result = Number('hello');
console.log(result); // NaN
result = Number(undefined);
console.log(result); // NaN
result = Number(NaN);
console.log(result); // NaN
Note: You can also generate numbers from strings using
parseInt(), parseFloat(), unary operator + and Math.floor(). For example,let result;
result = parseInt('20.01');
console.log(result); // 20
result = parseFloat('20.01');
console.log(result); // 20.01
result = +'20.01';
console.log(result); // 20.01
result = Math.floor('20.01');
console.log(result); // 20
2. Convert to String Explicitly:
To convert other data types to strings, you can use either
String() or toString(). For example,//number to string
let result;
result = String(324);
console.log(result); // "324"
result = String(2 + 4);
console.log(result); // "6"
//other data types to string
result = String(null);
console.log(result); // "null"
result = String(undefined);
console.log(result); // "undefined"
result = String(NaN);
console.log(result); // "NaN"
result = String(true);
console.log(result); // "true"
result = String(false);
console.log(result); // "false"
// using toString()
result = (324).toString();
console.log(result); // "324"
result = true.toString();
console.log(result); // "true"
Note:
String() takes null and undefined and converts them to string. However, toString() gives error when null are passed.3. Convert to Boolean Explicitly:
To convert other data types to a boolean, you can use Boolean().In JavaScript, undefined, null, 0, NaN, '' converts to false. For example,
let result;
result = Boolean('');
console.log(result); // false
result = Boolean(0);
console.log(result); // false
result = Boolean(undefined);
console.log(result); // false
result = Boolean(null);
console.log(result); // false
result = Boolean(NaN);
console.log(result); // false
All other values give
true. For example,result = Boolean(324);
console.log(result); // true
result = Boolean('hello');
console.log(result); // true
result = Boolean(' ');
console.log(result); // true
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