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HTML

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CSS

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JavaScript

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Babel includes JSX processing.

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HTML 

              
                <div id="tr-div-cpf">
    <input  type="number" 
            id="tr-cpf" 
            placeholder="CPF SEM PONTO E SEM TRAÇO"
            onkeypress="return apenasNumeros(event)"
    >
    <button onclick="validaCPF()">VALIDA CPF</button>
</div>
!

CSS 

              
                #tr-div-cpf,
    #tr-div-cpf input {
        width: 100%;
        margin-bottom: 25px;
    }

    #tr-div-cpf input {
        height: 50px;
        font-size: 1.5em;
    }

    #tr-div-cpf button {
        font-family: Ubuntu;
        font-size: 1.3em;
    }
!

JS 

              
                function apenasNumeros(e) {
        let tecla = (window.event) ? event.keyCode : e.which;
        if ((tecla > 47 && tecla < 58)) 
            return true;
        else
            return false;
    }

    function validaCPF() {
        let cpf = document.getElementById('tr-cpf').value;        
        if(cpf === '') {
            alert('Favor informe um CPF!');
            limpaInput();
        } else if (cpf.length < 11 || cpf.length > 11) {
            alert('Favor informe um CPF válido!');
            limpaInput();
        } else {            
            let strCPF = cpf.toString();
            let counter = 0;

            //VERIFICA SE OS 11 DÍGITOS SÃO IGUAIS COMO POR EXEMPLO EM 11111111111
            for(let i=0; i < strCPF.length - 1; i++) {
                if(strCPF[i] == strCPF[i+1]) {
                    strIgual = true;
                    counter++;
                } else {
                    strIgual = false;
                }                
            }

            //VERIFICA SE O CONTADOR É IGUAL 10: SE SIM, ENTÃO TODOS OS NÚMEROS SÃO IGUAIS, SENÃO VERIFICA SE O CPF É VÁLIDO SEGUNDO A FÓRMULA DE CÁLCULO DO DÍGITO VERIFICADOR
            if (counter == 10) {
                alert('CPF inválido');
                limpaInput();
            } else {
                let soma = 0;
                let resto;
                let primeiroDigito;
                let segundoDigito;

                //BLOCO DE VERIFICAÇÃO DO PRIMEIRO DÍGITO VERIFICADOR
                for(let i=1; i <= strCPF.length - 2; i++) {
                    soma = soma + parseInt(strCPF.substring(i-1, i)) * (11 - i);                    
                }
                resto = (soma * 10) % 11;
                
                if ((resto === 10) || (resto === 11)) {
                    resto = 0;
                }

                if (resto !== parseInt(cpf.substring(9, 10))) {
                    alert('PRIMEIRO Dígito verificador inválido!');
                } else {
                    primeiroDigito = true;
                }

                //BLOCO DE VERIFICAÇÃO DO SEGUNDO DÍGITO VERIFICADOR
                soma = 0;
                if(primeiroDigito) {
                    for (let i = 1; i <= strCPF.length - 1; i++) {
                        soma = soma + parseInt(strCPF.substring(i-1, i)) * (12 - i);
                    }
                    resto = (soma * 10) % 11;

                    if ((resto === 10) || (resto === 11)) { 
                        resto = 0;
                    }

                    if (resto !== parseInt(cpf.substring(10, 11))) {
                        alert('SEGUNDO Dígito verificador inválido!');
                    } else {
                        segundoDigito = true;
                    }
                }

                if( primeiroDigito && segundoDigito) {
                    alert('CPF VÁLIDO!!!!');                    
                }
            }
            
        }
    }

    function limpaInput() {
        document.getElementById('tr-cpf').value = '';
    }
!
999px

Console