Today #Day122 of #365DaysOfCode, Learning Essential JavaScript Interview Questions.
11. Assuming d is an “empty” object in scope, say: var d = {};
…what is accomplished using the following code?
[ 'zebra', 'horse' ].forEach(function(k) {
d[k] = undefined;
});
Ans,
var d = {};
["zebra", "horse"].forEach(function (k) {
d[k] = undefined;
});
console.log(d);
console.log(Object.keys(d));
console.log(Object.values(d));
console.log(Object.keys(["zebra", "horse"]));
console.log(Object.values(["zebra", "horse"]));
12. What will the code below output to the console and why?
var arr1 = "john".split('');
var arr2 = arr1.reverse();
var arr3 = "jones".split('');
arr2.push(arr3);
console.log("array 1: length=" + arr1.length + " last=" + arr1.slice(-1));
console.log("array 2: length=" + arr2.length + " last=" + arr2.slice(-1));
reverse() method returns the array itself.
for non-primitive data types their address will be referenced.
var arr1 = 'john'.split('')
var arr2 = arr1.reverse()
var arr3 = 'jones'.split('')
arr2.push(arr3)
console.log(`array 1: lenght = ${arr1.length}; last = ${arr1.slice(-1)}`);
console.log(`array 2: lenght = ${arr2.length}; last = ${arr2.slice(-1)}`);
console.log(arr1);
console.log(arr2);
console.log(arr3);
console.log(Object.keys(arr2));
console.log(Object.values(arr2));
console.log(arr2[3]);
console.log(arr2[4]);
console.log(arr2[4][0]);
console.log(arr2[4][1]);
console.log(arr2[4][2]);
console.log(arr2[4][3]);
output:
array 1: lenght = 5; last = j,o,n,e,s
array 2: lenght = 5; last = j,o,n,e,s
console.log(arr1);
["n", "h", "o", "j", Array(5)]
0: "n"
1: "h"
2: "o"
3: "j"
4: Array(5)
0: "j"
1: "o"
2: "n"
3: "e"
4: "s"
console.log(arr2);
["n", "h", "o", "j", Array(5)]
0: "n"
1: "h"
2: "o"
3: "j"
4: Array(5)
0: "j"
1: "o"
2: "n"
3: "e"
4: "s"
console.log(arr3);
(5) ["j", "o", "n", "e", "s"]
0: "j"
1: "o"
2: "n"
3: "e"
4: "s"
console.log(Object.keys(arr2));
(5) ["0", "1", "2", "3", "4"]
0: "0"
1: "1"
2: "2"
3: "3"
4: "4"
console.log(Object.values(arr2));
(5) ["n", "h", "o", "j", Array(5)]
0: "n"
1: "h"
2: "o"
3: "j"
4: Array(5)
0: "j"
1: "o"
2: "n"
3: "e"
4: "s"
console.log(arr2[3]);
j
console.log(arr2[4]);
(5) ["j", "o", "n", "e", "s"]
0: "j"
1: "o"
2: "n"
3: "e"
4: "s"
console.log(arr2[4][0]);
console.log(arr2[4][1]);
console.log(arr2[4][2]);
console.log(arr2[4][3]);
j
o
n
e
Conclusion
Learned and practiced Essential JavaScript Interview Questions involving topics like Objects & reverse() & non-primitive data types with their address reference.
Code
code
