Question: What is typeof []
Answer: Object. Actually Array is derived from Object. If you want to check array use Array.isArray(arr)
Question: What is typeof arguments
Answer: Object. arguments are array like but not array. it has length, can access by index but can’t push pop, etc.
Question: What is 2+true
Answer: 3. The plus operator between a number and a boolean or two boolean will convert boolean to number. Hence, true converts to 1 and you get result of 2+1
Question: What is '6'+9
Answer: 69. If one of the operands of the plus (+) operator is string it will convert other number or boolean to string and perform a concatenation. For the same reason, "2"+truewill return “2true”
Question: What is the value of 4+3+2+"1"
Answer: 91 . The addition starts from the left, 4+3 results 7 and 7+2 is 9. So far, the plus operator is performing addition as both the operands are number. After that 9 + “1” where one of the operands is string and plus operator will perform concatenation.
Question: What is the value of "1"+2+4
Answer: “124”. For this one “1” + 2 will produce “12” and “12”+4 will generates “124”.
Question: What is the value of -'34'+10
Answer: -24. minus(-) in front of a string is an unary operator that will convert the string to a number and will make it negative. Hence, -’34’ becomes, -34 and then plus (+) will perform simple addition as both the operands are number.
Question: What is the value of +'dude'
Answer: NaN. The plus (+) operator in front of a string is an unary operator that will try to convert the string to number. Here, JavaScript will fail to convert the “dude” to a number and will produce NaN.
Question: If you have var y = 1, x = y = typeof x; What is the value of x?
Answer: “undefined”
Question: for var a = (2, 3, 5); what is the value of a?
Answer: 5. The comma operator evaluates each of its operands (from left to right) and returns the value of the last operand. ref: MDN
Question: for var a = (1, 5 - 1) * 2 what is the value of a?
Answer: 8
Question: What is the value of !'bang'
Answer: false. ! is NOT. If you put ! in front of truthy values, it will return false. Using !! (double bang) is a tricky way to check anything truthy or falsy by avoiding implicit type conversion of == comparison.
Question: What is the value of parseFloat('12.3.4')
Answer: 12.3
Question: What is the value of Math.max([2,3,4,5]);
Answer: NaN
Question: 3 instanceof Number
Answer: false
Question:null == undefined
Answer: true
Question:What is the value of !!function(){};
Answer: true
Question: What is the value of typeof bar
Answer: “undefined”
Question: What is the value of typeof null
Answer: “object”
Question: If var a = 2, b =3 what would be value of a && b
Answer: 3
Question: What would be consoled var foo = 'outside'; function logIt(){console.log(foo); var foo = 'inside';} logIt();
Answer: undefined
Question: What is -5%2
Answer:-1. the result of remainder always get the symbol of first operand
Question: Why .1+.2 != .3
Answer:
Question: 42..toString()
Anwser: "42"
Question: 4.2..toString
Anwser: //SyntaxError: Unexpected token .
Question:42 . toString()
Anwser: "42"
Question: typeof(NaN)
Anwser:“number”
Question: 2 in [1,2]
Anwser: false. Because “in” returns whether a particular property/index available in the Object. In this case object has index 0 and 1 but don’t have 2. Hence you get false.
আল্লাহর নাম নিয়ে (আরম্ভ করছি), যিনি পরম করুণাময় 