Array splice removes all elements from array

Question

var currentAge = 26;
var maxAge = 100;
var amountPerDay = 30.50;

var calculation = (((maxAge - currentAge) * 365) * amountPerDay);
console.log(calculation);
var stringCalc = calculation.toString().split('').splice(2, 0, "9");
console.log(stringCalc);

console.log(stringCalc) shows an empty array. Does this have something to do with the toString method?

Note: I am trying to add the string "9" into the middle of the array, not remove anything from the array.

You are aware of the + operator in JavaScript, aren't you? Your code looks like it is for a write-code-that-is-impossible-to-read contest ;) — str
– str, Commented Feb 3, 2017 at 15:57
You're right, save for the two console statements, two lines of script is damn near impossible to read. Thanks for answering my question @str — Nyarlat-hotep
– Nyarlat-hotep, Commented Feb 3, 2017 at 15:59
I did not say that I don't understand the individual commands. But I have absolutely no clue what you are up to by converting an integer to a string, then to an array, then trying to change a single array item, and then cast the whole thing back to a string again. Just because it is possible doesn't make it good, understandable code. — str
– str, Commented Feb 3, 2017 at 16:02

Michael Maaß · Accepted Answer · 2017-02-03 16:06:39Z

5

The missing link in your understanding is the return value of splice, which are the deleted items.

var currentAge = 26;
var maxAge = 100;
var amountPerDay = 30.50;

var calculation = (((maxAge - currentAge) * 365) * amountPerDay);
console.log(calculation);
var stringCalc = calculation.toString().split('');
console.log(stringCalc);
// ["8", "2", "3", "8", "0", "5"]
console.log(stringCalc.splice(2, 0, "foo"));
// [] because no items were deleted, return value = array of deleted items
console.log(stringCalc)
// ["8", "2", "foo", 3", "8", "0", "5"]

answered Feb 3, 2017 at 16:06

Michael Maaß

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Comments

Feathercrown · Accepted Answer · 2017-02-03 15:59:56Z

0

var currentAge = 26;
var maxAge = 100;
var amountPerDay = 30.50;

var calculation = (((maxAge - currentAge) * 365) * amountPerDay);
console.log(calculation);
var stringCalc = calculation.toString().split('');
console.log(stringCalc);
stringCalc.splice(2, 0, "9");
console.log(stringCalc);

splice() returns the items taken out (in this case none), not the array after the splice takes place.

answered Feb 3, 2017 at 15:59

Feathercrown

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Comments

Andy Stannard · Accepted Answer · 2017-02-03 16:05:08Z

0

splice does not return an array just adds it into the existing array:

var currentAge = 26;
var maxAge = 100;
var amountPerDay = 30.50;

var calculation = (((maxAge - currentAge) * 365) * amountPerDay);
var numberArray = calculation.toString().split('')

numberArray.splice(2, 0, "9");
console.log(numberArray);

answered Feb 3, 2017 at 16:05

Andy Stannard

1,7113 gold badges18 silver badges32 bronze badges

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