Those scripts can be run on the input page, directly from the devtool console.
v=document.querySelector('pre').innerHTML.split('\n').map(x => parseInt(x, 10)).filter(x => !isNaN(x));v.forEach(x=>{v.forEach(y=>{if(x+y===2020)r=x*y})});r
v=document.querySelector('pre').innerHTML.split('\n').map(x => parseInt(x, 10)).filter(x => !isNaN(x));v.forEach(z=>{v.forEach(x=>{v.forEach(y=>{if(x+y+z===2020)r=x*y*z})})});r