add to your browsers developer console on https://www.websudoku.com/?level=1 and it will solve the puzzle

sudoku.js

function sudokuSolver(n, t) {
  let start = t;
  let count = n;
  const tableIndex = buildTableIndexes();

  let table = [];
  document.querySelectorAll("#puzzle_grid tr").forEach((row) => {
    let cells = [];
    for (var i = 0; i < row.cells.length; i++) {
      cells.push(row.cells[i])
    }
    table.push(cells);
  })

  let value;

  let tableValues = table.map((row) => {
    rowValues = row.map((cell) => {
      value = cell.firstChild.value
      if (value == "") {
        return null
      } else {
        return Number(value);
      }
    })
    return rowValues
  })

  let pv;
    tableValues = tableValues.map((row, rowIndex) => {
      newRow = row.map((cell, cellIndex) => {
        if (cell == null) {
          pv = onePossibleValue(rowIndex, cellIndex)
          if (pv) {
            table[rowIndex][cellIndex].firstChild.value = pv;
            return pv
          } else {
            return null
          }
        }
      })
      return newRow;
    })

  function onePossibleValue(row, cell) {
    let rowValues = tableValues[row];
    let columnValues = tableValues.map((row) => {
      return row[cell]
    })
    let boxValues = getBoxValues([row, cell]);
    let psbl = [];
    [1, 2, 3, 4, 5, 6, 7, 8, 9].forEach((num) => {
      if (!(rowValues.includes(num)) && !(columnValues.includes(num)) && !(boxValues.includes(num))) {
        psbl.push(num)
      }
    })
    if (psbl.length == 1) {
      return psbl[0]
    } else {
      return false
    }
  }

  function getBoxValues(index) {
    let box;
    tableIndex.forEach((table, i) => {
      table.forEach((l) => {
        if (l[0] == index[0] && l[1] == index[1]){
          box = tableIndex[i];
        }
      })
    })
    boxValues = box.map((cdn) => {
      return tableValues[cdn[0]][cdn[1]]
    })
    return boxValues;
  }


  function buildTableIndexes() {
    let indexes = [
      [0, 1, 2],
      [3, 4, 5],
      [6, 7, 8]
    ]

    let globalBoxIndex = []

    indexes.forEach((index) => {
      indexes.forEach((index2) => {
        index.forEach((i) => {
          index2.forEach((l) => {
            globalBoxIndex.push([i, l])
          })
        })
      })
    })

    let tableBoxes = [];
    let counter = 1;

    while(globalBoxIndex.length) {
      tableBoxes.push(globalBoxIndex.splice(0,9))
    }

    return tableBoxes;
  }
  count++;
  if (count == 20) {
    return console.log('Man this puzzle is too hard for me!')
  }

  if (tableValues.reduce((acc, val) => acc.concat(val), []).includes(null)) {
    sudokuSolver(count, start);
  } else {
    let end = new Date(Date.now())
    let timeDiff = (Math.abs(end.getTime() - start.getTime())/ 1000);
    console.log(`It took me ${timeDiff} seconds to solve this puzzle. Piece of cake!`)
  }
}
let t = new Date(Date.now())
sudokuSolver(0, t);