javascript - String interpolation on variable

Question

Say I have a variable str

var str = "123"

Now I could do console.log(`Hello ${str}`) and it will print Hello 123

Now I have another variable strnew

var strnew = 'Hello ${str}'

Note (based on answers/comments) - strnew is read from a file, so its always a string and cant be replaced with `

How do I console.log(...) to print Hello 123

Is it possible wihtout any kind of eval()

Answer 1

With something as simple as ${str} you can use a simple string replacement:

var template = (tpl, args) => tpl.replace(/${(w+)}/g, (_, v) => args[v]);

var tpl = 'Hello ${str} and ${other}';

console.log(template(tpl, {str: 'foo', other: 'bar'}));