window.onload = function () {
    document.getElementById('input').addEventListener('change', getFile)
}

function getFile(){
    const input = event.target
    if ('files' in input && input.files.length > 0) {
        placeFileContent(document.getElementById('content'), input.files[0])
    }
}

function placeFileContent(target, file) {
	readFileContent(file).then(content => {
        target.value = content
    }).catch(error => console.log(error))
}

function readFileContent(file) {
	const reader = new FileReader()
    return new Promise((resolve, reject) => {
        reader.onload = event => resolve(event.target.result)
        reader.onerror = error => reject(error)
        reader.readAsText(file)
    })
}