Issue when implementing a set text method in protractor

In below code, I can set text ok. However, the output in console log always is Set Text '' UnSuccessfully!

setText(textSet) {
    let self = this;
    let result = "";
    this.clear()
        .then(function () {
            return self.sendKeys(textSet);
        })
        .then(function () {
            return self.getText();

        })
        .then(function (textGet) {

            console.log("Set Text '"+textGet+"' UnSuccessfully !");
        })



}

via Mike