Js to implement call,apply,bind functions

Call function implementation

Function.prototype.ltCall = function(thisArg, ... arr) {
        var result = undefined;
        var fn = this;
        // Determine if thisArg passed is null or undefind
        thisArg = thisArg ? Object(thisArg) : window;
        // define a symbol variable to prevent thisArg from having the same attribute name
        var symbol = Symbol(a);// Add a symbol attribute to thisArg
        thisArg[symbol] = fn;
        // Check whether arR is null
        arr = arr ? arr : [];
        // Get the symbol attribute on the object
        var symbols = Object.getOwnPropertySymbols(thisArg);
        for (key of symbols) {
            // Point this to thisArg via an implicit callresult = thisArg[key](... arr);// When the function is called, delete the fn attribute
            delete thisArg[key];
        }
        return result;
    };

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Apply function implementation

Function.prototype.ltapply = function(thisArg, arr) {
        var result = undefined;
        var fn = this;
        thisArg = thisArg ? Object(thisArg) : window;
        thisArg.fn = fn;
        // define a symbol variable to prevent thisArg from having the same attribute name
        var symbol = Symbol(a);// Add a symbol attribute to thisArg
        thisArg[symbol] = fn;
        // Check whether arR is null
        arr = arr ? arr : [];
        // Get the symbol attribute on the object
        var symbols = Object.getOwnPropertySymbols(thisArg);
        for (key of symbols) {
            // Point this to thisArg via an implicit callresult = thisArg[key](... arr);// When the function is called, delete the fn attribute
            delete thisArg[key];
        }
        return result;
    };
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Bind function implementation

Function.prototype.ltbind = function(thisArg, ... arr) {
        var fn = this;
        thisArg = thisArg ? Object(thisArg) : window;
        // define a symbol variable to prevent thisArg from having the same attribute name
        var symbol = Symbol(a);// Add a symbol attribute to thisArg
        thisArg[symbol] = fn;
        arr = arr ? arr : [];

        function proxyFn() {
            var result = undefined;
            ThisArg gets all symbol attributes on thisArg
            var symbols = Object.getOwnPropertySymbols(thisArg);
            for (key of symbols) {
                // Point this to thisArg via an implicit callresult = thisArg[key](... arr);// When the function is called, delete the fn attribute
                delete thisArg[key];
                returnresult; }}return proxyFn;
    };
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• Thank you very muchWang hong yuanThe teacher’sDeep dive into JavaScript advanced syntaxLet me learn a lotJavaScriptKnowledge.