Day 10.md

Day 10 : Introduction , Types and Coercion

Today, I had an exciting start as I delved into the "Deep JavaScript Foundations, v3" course. We began with an introduction to the course, and then we dived into the topics of types and coercion in JavaScript.

Lessons Summary

• Most developers beileve that everything in JS is object , but the fact is most values in JS can behave like objects.
• We can use "typeof()" method that takes a one argument to return the type of this argument.
• There is a different types of data in JS such as primitive data types , object, bigint and null.
• "undefinde" means there is a variable but doesnt have a value ,but "undeclared" means that is not been created.
• NaN means invalid number but is the number.
• There is a many abstract operation to coversion between data types .
• The coersion is the automatic or implicit conversion of values from one data type to another.

Coding Examples

// using typeof() method 
var v;
typeof(v); // undefined

// using isNaN() method
Number.isNaN("my string "); // false

// using objectis() exercise 
 define polyfill for `Object.is(..)`
if (!Object.is() || true) {
    Object.is = function (x, y) {
        var XnegativeZero = isNegativeZero(x);
        var YnegativeZero = isNegativeZero(y);

        if (XnegativeZero || YnegativeZero) {
            return XnegativeZero && YnegativeZero;
        }

        else if (isItNaN(x) && isItNaN(y)) {
            return true;
        }
        
        else{
            return x===y;
        }

        function isNegativeZero(v) {
            return v === 0 && 1 / v === -Infinity;
        }

        function isItNaN(v) {
            return v !== v;
        }
    };
}

// Coercion: using string concatenation (number to string)
var age=15;
var myName="mostafa";
console.log("Hi"+myName + age); // "Hi mostafa 15"

Coding Exercises

Week 3 Day 1 Exercise

/// exercise one

function convertStringToNumber(input) {
    if (typeof input === "string") {
        return +input;
    }
    else {
        return {
            value: input,
            type: typeof (input)
        };
    }
}

//exercise two
const checkNaN = (value) => {
    return value !== value;
}


//exercise three
function isEmptyValue(value) {
    return value === undefined || value === null || value === '';
}


// exercise four
function compareObjects(input1, input2) {
    if (typeof input1 !== "object" || typeof input2 !== "object") {
        return [input1, input2];
    }

    const keys1 = Object.keys(input1);
    const keys2 = Object.keys(input2);

    if (keys1.length !== keys2.length)
        return false;

    for (const key of keys1) {
        if (input1[key] !== input2[key])
            return false;
    }

    return true;
}


// exercise five


const complexCoercion = (input) => {
    if (typeof input === 'number') {
      return Boolean(String(input));
    } else if (typeof input === 'string') {
      return Boolean(input);
    } else if (input === null || input === undefined) {
      return false;
    } else {
      return input;
    }
  };