sforce.opencti.saveLog() and sforce.opencti.screenPop() methods can be used to create and open Case record in Salesforce using Open CTI.
Sample Code:
sforce.opencti.saveLog( {
value: {
entityApiName : "Case",
Subject : "Testing",
Priority : "Low",
Origin : "Phone"
},
callback: function( result ) {
console.log(
'Result is',
JSON.stringify( result )
);
console.log(
'Record Id is',
result.returnValue.recordId
);
sforce.opencti.screenPop( {
type : sforce.opencti.SCREENPOP_TYPE.SOBJECT,
params : {
recordId : result.returnValue.recordId
},
callback : function( result ) {
console.log(
'Result is',
JSON.stringify( result )
)
}
} );
}
} ); 
