d8 is a minimal shell for running JavaScript programs using V8. Does the implementation of console.log in d8 support format specifiers/characters? I tried to use a format specifier, and it printed the specifier and the variable value (as shown below).
d8> for (i = 0; i < 10; i++) {console.log('Number is %d', i);}
Number is %d 0
Number is %d 1
Number is %d 2
Number is %d 3
Number is %d 4
Number is %d 5
Number is %d 6
Number is %d 7
Number is %d 8
Number is %d 9
undefined
I see a similar question here: https://github.com/nodejs/node/issues/10292 ... Any insight would be helpful.
As you can see from your experiment, d8 does not support format specifiers. It wouldn't want to support anything that's not legal JavaScript.
Speaking of which: JavaScript has "template literals" since a while. So without placing any requirements on d8 or console.log, anywhere you have strings you can do:
let i = 42;
console.log(`Number is ${i}`);
let just_a_string = `1 + 2 = ${1+2}`;
console.log(just_a_string);
console.assert(just_a_string === "1 + 2 == 3");
If you were hoping for more advanced formatting, like C-style %5d, AFAIK you'll have to build that yourself. If you're interested in floating-point numbers, .toFixed and .toPrecision might be helpful.